func_code_string: #include <bits/stdc++.h>   using namespace std;   string op;   bool check(int l, int r) {     char c;     cout <<  ?   << l <<     << r << endl;     cin >> c;     return c ==  x ;   }   int main() {     while (cin >> op) {       if (op ==  end ) {         return 0;       }       int l = 1, r = 2;       while (1) {         if (check(l, r)) break;         l <<= 1, r <<= 1;       }       while (l + 1 < r) {         int mid = (l + r) >> 1;         if (check(l - 1, mid))           r = mid;         else           l = mid + 1;       }       if (l == 1 && r == 2) {         if (check(2, 3))           cout <<  ! 1  << endl;         else           cout <<  ! 2  << endl;       } else {         if (l == r)           cout <<  !   << l << endl;         else {           if (check(l, l + 1))             cout <<  !   << l + 1 << endl;           else             cout <<  !   << l << endl;         }       }     }   }   