View Compilation Error

0_0_33386943_19191.cpp:4:1: error: '_int64' does not name a type
 _int64 f(int n) {
 ^
0_0_33386943_19191.cpp: In function 'int main()':
0_0_33386943_19191.cpp:17:14: error: 'f' was not declared in this scope
   cout << f(n) << endl;
              ^