func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   void read(T &x) {     x = 0;     bool f = 0;     char c = getchar();     for (; !isdigit(c); c = getchar())       if (c ==  - ) f = 1;     for (; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);     if (f) x = -x;   }   template <typename F>   inline void write(F x, char ed =   n ) {     static short st[30];     short tp = 0;     if (x < 0) putchar( - ), x = -x;     do st[++tp] = x % 10, x /= 10;     while (x);     while (tp) putchar( 0  | st[tp--]);     putchar(ed);   }   template <typename T>   inline void Mx(T &x, T y) {     x < y && (x = y);   }   template <typename T>   inline void Mn(T &x, T y) {     x > y && (x = y);   }   const int N = 50005;   int a[N], n;   long long ask(int l, int r) {     cout <<  ?   << l <<     << r << endl;     fflush(stdout);     long long t;     cin >> t;     return t;   }   int main() {     read(n);     long long t1 = ask(1, 2), t2 = ask(1, 3), t3 = ask(2, 3);     a[3] = t2 - t1, a[2] = t3 - a[3], a[1] = t1 - a[2];     for (int i = 4; i <= n; i++) a[i] = ask(i - 1, i) - a[i - 1];     cout <<  !  ;     for (int i = 1; i <= n; i++) cout << a[i] <<    ;     fflush(stdout);     return 0;   }   