View Compilation Error

0_0_22309066_28766.cpp: In function 'int main()':
0_0_22309066_28766.cpp:24:2: error: '_int64' was not declared in this scope
  _int64 n;
  ^
0_0_22309066_28766.cpp:25:25: error: 'n' was not declared in this scope
  while (scanf("%I64d", &n) != EOF)
                         ^
0_0_22309066_28766.cpp:34:10: error: expected ';' before 'sum'
   _int64 sum = a[0].per;
          ^
0_0_22309066_28766.cpp:43:6: error: 'sum' was not declared in this scope
      sum += (a[j].numbers / a[j].per)*(a[i].per+a[j].per) ;
      ^
0_0_22309066_28766.cpp:50:6: error: 'sum' was not declared in this scope
      sum += (a[i].numbers / a[i].per)*(a[j].per+a[i].per);
      ^
0_0_22309066_28766.cpp:57:21: error: 'sum' was not declared in this scope
   printf("%I64d\n", sum);
                     ^