func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     map<int, vector<int>> mp;     for (int i = 1; i <= n; i++) {       int a;       cin >> a;       mp[a].push_back(i);     }     vector<pair<int, int>> ans;     int cnt = 0;     for (auto ele : mp) {       int a = ele.first;       vector<int> pos = ele.second;       if (pos.size() == 1) {         ans.push_back({a, 0});       } else {         int diff = pos[1] - pos[0];         bool can = true;         for (int i = 2; i <= pos.size() - 1; i++) {           if (pos[i] - pos[i - 1] != diff) {             can = false;             break;           }         }         if (can) {           ans.push_back({a, diff});         }       }     }     cout << ans.size() << endl;     for (auto& ele : ans) {       cout << ele.first <<     << ele.second << endl;     }     return 0;   }   