View Compilation Error

0_0_35173418_26952.cpp: In function 'int main()':
0_0_35173418_26952.cpp:6:2: error: '_int64' was not declared in this scope
  _int64 a, b, c;
  ^
0_0_35173418_26952.cpp:7:30: error: 'a' was not declared in this scope
  while (scanf("%I64X%I64X", &a, &b) != EOF)
                              ^
0_0_35173418_26952.cpp:7:34: error: 'b' was not declared in this scope
  while (scanf("%I64X%I64X", &a, &b) != EOF)
                                  ^
0_0_35173418_26952.cpp:9:3: error: 'c' was not declared in this scope
   c = a + b;
   ^