/in/foo.cc: In function 'int main()':
/in/foo.cc:32:16: error: 'scanf' was not declared in this scope
  scanf("%d", &n);
                ^
/in/foo.cc:61:31: error: 'printf' was not declared in this scope
   printf("%d %d", fenzi, fenmu); //1 5/6正确  7/12没加5/6
                               ^