func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T, typename U>   inline void smin(T &a, const U &b) {     if (a > b) a = b;   }   template <typename T, typename U>   inline void smax(T &a, const U &b) {     if (a < b) a = b;   }   template <typename T>   inline void gn(T &first) {     char c, sg = 0;     while (c = getchar(), (c >  9  || c <  0 ) && c !=  - )       ;     for ((c ==  -  ? sg = 1, c = getchar() : 0), first = 0; c >=  0  && c <=  9 ;          c = getchar())       first = (first << 1) + (first << 3) + c -  0 ;     if (sg) first = -first;   }   template <class T, class T1>   inline void gn(T &first, T1 &second) {     gn(first);     gn(second);   }   template <class T, class T1, class T2>   inline void gn(T &first, T1 &second, T2 &z) {     gn(first);     gn(second);     gn(z);   }   template <typename T>   inline void print(T first) {     if (first < 0) {       putchar( - );       return print(-first);     }     if (first < 10) {       putchar( 0  + first);       return;     }     print(first / 10);     putchar(first % 10 +  0 );   }   template <typename T>   inline void println(T first) {     print(first), putchar(  n );   }   template <typename T>   inline void printsp(T first) {     print(first), putchar(   );   }   template <class T, class T1>   inline void print(T first, T1 second) {     printsp(first), println(second);   }   template <class T, class T1, class T2>   inline void print(T first, T1 second, T2 z) {     printsp(first), printsp(second), println(z);   }   int power(int a, int b, int m, int ans = 1) {     for (; b; b >>= 1, a = (long long)a * a % m)       if (b & 1) ans = (long long)ans * a % m;     return ans;   }   pair<int, int> p[50010];   int f[50010];   void go(int first) {     printf( ? %d n , first);     fflush(stdout);     gn(p[first].first, p[first].second);   }   void end(int first) {     printf( ! %d n , first);     exit(0);   }   int main() {     int n, id, first;     gn(n, id, first);     for (int i = 1; i <= n; i++) f[i] = i;     srand(time(0));     random_shuffle(f + 1, f + n + 1);     go(id);     if (p[id].first >= first) end(p[id].first);     int N = min(n, 1000);     for (int i = 1; i <= N; i++) {       go(f[i]);       int u = p[f[i]].first;       if (u < first && u > p[id].first) id = f[i];     }     while (1) {       if (!p[id].second) go(id);       if (p[id].first >= first) end(p[id].first);       if (p[id].second == -1) end(-1);       id = p[id].second;     }   }   