#include <bits/stdc++.h> using namespace std; int main() { int b[1001] = {0}; int n; cin >> n; for (int i = 1; i <= n; i++) { int x; cin >> x; b[x] = b[x] + 1; } for (int i = 1; i <= 100; i++) { if (b[i] % 2 == 1) { cout << i; break; } } return 0; }