func_code_string: #include <bits/stdc++.h>   using namespace std;   int inX[1000001] = {0};   int used[1000001] = {0};   vector<int> ans;   int main() {     int n;     scanf( %d , &n);     vector<int> given(n, 0);     for (int i = 0; i < n; i++) {       scanf( %d , &given[i]);       inX[given[i]] = 1;       used[given[i]] = 1;     }     vector<int> pairLeft;     int reqdPairs = 0;     for (int i = 1; i <= 1000000; i++) {       if (inX[i]) {         if (inX[1000000 + 1 - i] == 0) {           used[1000000 + 1 - i] = 1;           ans.push_back(1000000 + 1 - i);         } else {           reqdPairs += 1;         }       } else {         if (inX[i] == inX[1000000 + 1 - i]) pairLeft.push_back(i);       }     }     for (int i = 0; 2 * i < reqdPairs; i++) {       ans.push_back(pairLeft[i]);       ans.push_back(1000000 + 1 - pairLeft[i]);     }     printf( %d n , (int)ans.size());     for (int i = 0; i < (int)ans.size(); i++) printf( %d  , ans[i]);     return 0;   }   