View Compilation Error

0_0_37909583_29834.cpp:2:1: error: '__int64' does not name a type
 __int64 cal(int n, int m){
 ^
0_0_37909583_29834.cpp: In function 'int main()':
0_0_37909583_29834.cpp:12:2: error: '__int64' was not declared in this scope
  __int64 ans;
  ^
0_0_37909583_29834.cpp:13:22: error: 'scanf' was not declared in this scope
  while(scanf("%d", &n) == 1){
                      ^
0_0_37909583_29834.cpp:14:3: error: 'ans' was not declared in this scope
   ans = 0;
   ^
0_0_37909583_29834.cpp:16:29: error: 'cal' was not declared in this scope
    ans += (i - 1) * cal(n, i);
                             ^
0_0_37909583_29834.cpp:17:24: error: 'printf' was not declared in this scope
   printf("%I64d\n", ans);
                        ^
0_0_37909583_29834.cpp:19:10: error: expected '}' at end of input
  return 0;
          ^