func_code_string: #include <bits/stdc++.h>   using namespace std;   bool deb = false;   int n;   vector<int> p, b;   void init() {     if (!deb) return;     p.resize(n);     for (auto& x : p) cin >> x;     b.resize(n);     for (int i = 0; i < n; ++i) b[p[i]] = i;   }   int get(int i, int j) {     if (deb) return p[i] ^ b[j];     cout <<  ?   << i <<     << j << endl;     int x;     cin >> x;     if (x == -1) exit(0);     return x;   }   void ans(int cnt, vector<int> p) {     cout <<  ! n ;     cout << cnt << endl;     for (int x : p) cout << x <<    ;     cout << endl;   }   int main() {     cin >> n;     init();     vector<int> a(n);     for (int i = 0; i < n; ++i) a[i] = get(0, i);     vector<int> x(n);     for (int i = 0; i < n; ++i) x[i] = get(i, 0);     int cnt = 0;     vector<int> pans;     for (int i = 0; i < n; ++i) {       vector<int> b(n);       for (int j = 0; j < n; ++j) b[j] = i ^ a[j];       vector<int> arr(n);       for (int i : b)         if (i < n) ++arr[i];       if (count(arr.begin(), arr.end(), 1) != n) continue;       vector<int> p(n);       for (int j = 0; j < n; ++j) p[b[j]] = j;       bool f = true;       for (int j = 0; j < n; ++j)         if ((p[j] ^ b[0]) != x[j]) f = false;       if (f) ++cnt, pans = p;     }     ans(cnt, pans);   }   