func_code_string: #include <bits/stdc++.h>   using namespace std;   int n;   long long ar[100100];   int main() {     cin >> n;     for (int i = 0; i < n; i++) {       cin >> ar[i];     }     sort(ar, ar + n);     long long dif1 = ar[1] - ar[0], dif2 = -1;     int cnt1 = 0, cnt2 = 0;     if (n == 1) {       cout << -1 << endl;       return 0;     } else if (n == 2) {       if (ar[0] == ar[1]) {         cout << 1 << endl << ar[0];         return 0;       } else {         if ((ar[0] + ar[1]) % 2 == 0) {           cout << 3 << endl                << ar[0] - (ar[1] - ar[0]) <<     << (ar[1] + ar[0]) / 2 <<                    << ar[1] + (ar[1] - ar[0]) << endl;           return 0;         } else {           cout << 2 << endl                << ar[0] - (ar[1] - ar[0]) <<     << ar[1] + (ar[1] - ar[0])                << endl;           return 0;         }       }     } else {       set<long long> nd;       set<long long> ans;       for (int i = 1; i < n; i++) {         nd.insert(ar[i] - ar[i - 1]);       }       if (nd.size() > 2) {         cout << 0 << endl;       } else if (nd.size() == 1) {         ans.insert(ar[0] - (ar[1] - ar[0]));         ans.insert(ar[n - 1] + (ar[1] - ar[0]));         cout << ans.size() << endl;         for (auto it : ans) {           cout << it << endl;         }       } else {         int ls1 = -1, ls2 = -1;         dif1 = *nd.begin();         dif2 = *(++nd.begin());         if (dif1 != 2 * dif2 && dif2 != 2 * dif1) {           cout << 0 << endl;           return 0;         }         for (int i = 1; i < n; i++) {           if (ar[i] - ar[i - 1] == dif1) {             cnt1++;             ls1 = i;           } else {             cnt2++;             ls2 = i;           }         }         if (cnt1 == 1 && dif1 % 2 == 0 && dif1 > dif2) {           cout << 1 << endl;           cout << ar[ls1 - 1] + dif2 << endl;           return 0;         }         if (cnt2 == 1 && dif2 % 2 == 0 && dif1 < dif2) {           cout << 1 << endl;           cout << ar[ls2 - 1] + dif1 << endl;           return 0;         }         cout << 0 << endl;       }     }     return 0;   }   