View Compilation Error

0_0_23842401_18602.cpp:2:1: error: '_int64' does not name a type
 _int64 fun(int x)
 ^
0_0_23842401_18602.cpp: In function 'int main()':
0_0_23842401_18602.cpp:19:26: error: 'fun' was not declared in this scope
   printf("%I64d\n",(fun(x)/(fun(y)*fun(x-y))));
                          ^