# -*- coding: utf-8 -*-
# URI Judge - Problema 1007

a = int(input())
b = int(input())
c = int(input())
d = int(input())

diferenca = ((a * b) - (c * d))

print("DIFERENCA =", diferenca)

# -*- coding: utf-8 -*-
# URI Judge - Problema 1007

a = int(input())
b = int(input())
c = int(input())
d = int(input())

diferenca = ((a * b) - (c * d))

print("DIFERENCA =", diferenca)

# -*- coding: utf-8 -*- # URI Judge - Problema 1007