Question:
Who was the head of Berlin in Mar, 2015?

Context:
 Ernst Reuter is the head of the government of Berlin from Dec, 1948 to Oct, 1953. 
 Franz Amrehn is the head of the government of Berlin from Aug, 1957 to Oct, 1957. 
 Michael Müller is the head of the government of Berlin from Dec, 2014 to Dec, 2021. 
 Otto Suhr is the head of the government of Berlin from Jan, 1955 to Aug, 1957. 
 Klaus Schütz is the head of the government of Berlin from Oct, 1967 to May, 1977. 
 Hans-Jochen Vogel is the head of the government of Berlin from Jan, 1981 to Jun, 1981. 
 Willy Brandt is the head of the government of Berlin from Oct, 1957 to Dec, 1966. 
 Richard von Weizsäcker is the head of the government of Berlin from Jun, 1981 to Feb, 1984. 
 Dietrich Stobbe is the head of the government of Berlin from May, 1977 to Jan, 1981. 
 Klaus Wowereit is the head of the government of Berlin from Jun, 2001 to Dec, 2014. 
 Walter Momper is the head of the government of Berlin from Mar, 1989 to Jan, 1991. 
 Walther Schreiber is the head of the government of Berlin from Oct, 1953 to Jan, 1955. 
 Eberhard Diepgen is the head of the government of Berlin from Jan, 1991 to Jun, 2001. 
 Franziska Giffey is the head of the government of Berlin from Dec, 2021 to Dec, 2022. 
 Heinrich Albertz is the head of the government of Berlin from Dec, 1966 to Oct, 1967.

Answer:
Question:
Who was the head of Berlin in Mar, 2015?

Context:
 Ernst Reuter is the head of the government of Berlin from Dec, 1948 to Oct, 1953. 
 Franz Amrehn is the head of the government of Berlin from Aug, 1957 to Oct, 1957. 
 Michael Müller is the head of the government of Berlin from Dec, 2014 to Dec, 2021. 
 Otto Suhr is the head of the government of Berlin from Jan, 1955 to Aug, 1957. 
 Klaus Schütz is the head of the government of Berlin from Oct, 1967 to May, 1977. 
 Hans-Jochen Vogel is the head of the government of Berlin from Jan, 1981 to Jun, 1981. 
 Willy Brandt is the head of the government of Berlin from Oct, 1957 to Dec, 1966. 
 Richard von Weizsäcker is the head of the government of Berlin from Jun, 1981 to Feb, 1984. 
 Dietrich Stobbe is the head of the government of Berlin from May, 1977 to Jan, 1981. 
 Klaus Wowereit is the head of the government of Berlin from Jun, 2001 to Dec, 2014. 
 Walter Momper is the head of the government of Berlin from Mar, 1989 to Jan, 1991. 
 Walther Schreiber is the head of the government of Berlin from Oct, 1953 to Jan, 1955. 
 Eberhard Diepgen is the head of the government of Berlin from Jan, 1991 to Jun, 2001. 
 Franziska Giffey is the head of the government of Berlin from Dec, 2021 to Dec, 2022. 
 Heinrich Albertz is the head of the government of Berlin from Dec, 1966 to Oct, 1967.

Answer:
user
Michael Müller
assistant
Question:
Who was the head of Berlin in Mar, 2015?

Context:
 Ernst Reuter is the head of the government of Berlin from Dec, 1948 to Oct, 1953. 
 Franz Amrehn is the head of the government of Berlin from Aug, 1957 to Oct, 1957. 
 Michael Müller is the head of the government of Berlin from Dec, 2014 to Dec, 2021. 
 Otto Suhr is the head of the government of Berlin from Jan, 1955 to Aug, 1957. 
 Klaus Schütz is the head of the government of Berlin from Oct, 1967 to May, 1977. 
 Hans-Jochen Vogel is the head of the government of Berlin from Jan, 1981 to Jun, 1981. 
 Willy Brandt is the head of the government of Berlin from Oct, 1957 to Dec, 1966. 
 Richard von Weizsäcker is the head of the government of Berlin from Jun, 1981 to Feb, 1984. 
 Dietrich Stobbe is the head of the government of Berlin from May, 1977 to Jan, 1981. 
 Klaus Wowereit is the head of the government of Berlin from Jun, 2001 to Dec, 2014. 
 Walter Momper is the head of the government of Berlin from Mar, 1989 to Jan, 1991. 
 Walther Schreiber is the head of the government of Berlin from Oct, 1953 to Jan, 1955. 
 Eberhard Diepgen is the head of the government of Berlin from Jan, 1991 to Jun, 2001. 
 Franziska Giffey is the head of the government of Berlin from Dec, 2021 to Dec, 2022. 
 Heinrich Albertz is the head of the government of Berlin from Dec, 1966 to Oct, 1967.

Answer:
user
Eberhard Diepgen
Hans-Jochen Vogel
Otto Suhr
Klaus Schütz
Richard von Weizsäcker
Franz Amrehn
Willy Brandt
Walter Momper
Franziska Giffey
Klaus Wowereit
Ernst Reuter
Walther Schreiber
Dietrich Stobbe
Heinrich Albertz
assistant
Question:
Who was the head of Berlin in Mar, 2015?

Context:
 Ernst Reuter is the head of the government of Berlin from Dec, 1948 to Oct, 1953. 
 Franz Amrehn is the head of the government of Berlin from Aug, 1957 to Oct, 1957. 
 Michael Müller is the head of the government of Berlin from Dec, 2014 to Dec, 2021. 
 Otto Suhr is the head of the government of Berlin from Jan, 1955 to Aug, 1957. 
 Klaus Schütz is the head of the government of Berlin from Oct, 1967 to May, 1977. 
 Hans-Jochen Vogel is the head of the government of Berlin from Jan, 1981 to Jun, 1981. 
 Willy Brandt is the head of the government of Berlin from Oct, 1957 to Dec, 1966. 
 Richard von Weizsäcker is the head of the government of Berlin from Jun, 1981 to Feb, 1984. 
 Dietrich Stobbe is the head of the government of Berlin from May, 1977 to Jan, 1981. 
 Klaus Wowereit is the head of the government of Berlin from Jun, 2001 to Dec, 2014. 
 Walter Momper is the head of the government of Berlin from Mar, 1989 to Jan, 1991. 
 Walther Schreiber is the head of the government of Berlin from Oct, 1953 to Jan, 1955. 
 Eberhard Diepgen is the head of the government of Berlin from Jan, 1991 to Jun, 2001. 
 Franziska Giffey is the head of the government of Berlin from Dec, 2021 to Dec, 2022. 
 Heinrich Albertz is the head of the government of Berlin from Dec, 1966 to Oct, 1967.

Answer:
user
Michael Müller
assistant