#include<bits/stdc++.h> using namespace std; int main() { int n; cin >>n; int a[101] = {0}; for (int i = 0; i < n; i++) { int q; cin >> q; a[q] = a[q] + 1; } int w = 0; for (int i = 1; i <= 100; i++) { if (a[i] == 1) { w = i; break; } } cout << w << endl; return 0; }