View Compilation Error

0_0_13302642_3097.cpp:3:1: error: '_int64' does not name a type
 _int64 fib(_int64 a);
 ^
0_0_13302642_3097.cpp: In function 'int main()':
0_0_13302642_3097.cpp:6:5: error: '_int64' was not declared in this scope
     _int64 a;
     ^
0_0_13302642_3097.cpp:7:16: error: 'a' was not declared in this scope
     while(cin>>a)
                ^
0_0_13302642_3097.cpp:11:20: error: 'fib' was not declared in this scope
         cout<<fib(a)<<endl;
                    ^
0_0_13302642_3097.cpp: At global scope:
0_0_13302642_3097.cpp:15:1: error: '_int64' does not name a type
 _int64 fib(_int64 a)
 ^