func_code_string: #include <bits/stdc++.h>   using namespace std;   class Solver {    public:     void input() {       cin >> n;       a.resize(n);       for (int i = 0; i < n; i++) {         cin >> a[i];       }     }     void print() { cout << solve() << endl; }       private:     vector<int> a;     int n;     long long f(int x) {       long long ans = 0;       for (int i = 0; i < n; i++) {         int j = lower_bound(a.begin(), a.end(), x - a[i]) - a.begin();         if (i < j) {           ans += j - i - 1;         } else {           break;         }       }       return ans;     }     int solve() {       int ans = 0;       for (int i = 30; i >= 0; i--) {         for (int j = 0; j < n; j++) {           a[j] = (a[j] & ((1 << (i + 1)) - 1));         }         sort(a.begin(), a.end());         long long cur = f(1 << (i + 1)) - f(1 << i);         cur += f(1 << (i + 2)) - f((1 << i) + (1 << (i + 1)));         if (cur & 1) {           ans = (ans | (1 << i));         }       }       return ans;     }   };   int main() {     ios::sync_with_stdio(false);     Solver solver;     solver.input();     solver.print();     return 0;   }   