View Compilation Error

0_0_31524632_1542.cpp: In function 'int main()':
0_0_31524632_1542.cpp:4:2: error: '_int64' was not declared in this scope
  _int64 a,b,c;
  ^
0_0_31524632_1542.cpp:5:29: error: 'a' was not declared in this scope
  while(scanf("%I64X %I64X",&a,&b)!=EOF)
                             ^
0_0_31524632_1542.cpp:5:32: error: 'b' was not declared in this scope
  while(scanf("%I64X %I64X",&a,&b)!=EOF)
                                ^
0_0_31524632_1542.cpp:7:3: error: 'c' was not declared in this scope
   c=a+b;
   ^