/in/foo.cc: In function 'int main()':
/in/foo.cc:30:31: error: 'scanf' was not declared in this scope
     scanf("%lld%lld" , &a , &b) , a -- ;
                               ^
/in/foo.cc:36:33: error: 'sort' was not declared in this scope
     sort(w + 1 , w + n + 1 , cmp);
                                 ^
/in/foo.cc:39:34: error: 'printf' was not declared in this scope
     printf("%lld\n" , b - a - ans);
                                  ^