Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_54058 ( "Name" text, "Tenure Begin" text, "Tenure End" real, "British monarch" text, "Czechoslovak president" text )

### Question ###
Who was the President of Czechoslovakia when an ambassador's tenure began in 1950?

### Accurate SQL ###

SELECT "Czechoslovak president" FROM table_54058 WHERE "Tenure Begin" = '1950'