View Compilation Error

0_0_16828948_31923.cpp: In function 'int main()':
0_0_16828948_31923.cpp:5:2: error: '_int64' was not declared in this scope
  _int64 n,a;
  ^
0_0_16828948_31923.cpp:8:23: error: 'n' was not declared in this scope
  while(scanf("%I64d",&n)!=EOF)
                       ^
0_0_16828948_31923.cpp:12:19: error: 'a' was not declared in this scope
    scanf("%I64d",&a);
                   ^