View Compilation Error

0_0_36282367_21945.cpp: In function 'void sum(std::string, std::string)':
0_0_36282367_21945.cpp:14:2: error: 'longlong' was not declared in this scope
  longlong int i;
  ^
0_0_36282367_21945.cpp:17:6: error: 'i' was not declared in this scope
  for(i=a.length()-1;i>=0;i--){
      ^