View Compilation Error

0_0_16264689_18007.cpp: In function 'int main()':
0_0_16264689_18007.cpp:26:10: error: 'int_128' was not declared in this scope
   ans = (int_128)n * (n - 1) * (n - 2) * (n - 3) / 24 + n;
          ^