View Compilation Error

0_0_29993730_2723.cpp:3:1: error: '_int128' does not name a type
 _int128 _a, _b, _m;
 ^
0_0_29993730_2723.cpp: In function 'long long int mul(long long int, long long int, long long int)':
0_0_29993730_2723.cpp:5:2: error: '_a' was not declared in this scope
  _a = a;
  ^
0_0_29993730_2723.cpp:6:2: error: '_b' was not declared in this scope
  _b = b;
  ^
0_0_29993730_2723.cpp:7:2: error: '_m' was not declared in this scope
  _m = m;
  ^