#include <iostream>
#include <sstream>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <numeric>
#include <vector>
#include <string>
#include <set>
#include <map>

using namespace std;
#define ll long long
void sherry()
{
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#endif
}
bool comp(pair<int, int> a, pair<int, int> b)
{
    return a.second < b.second;
}
int main()
{
    sherry();
    ll n;
    cin >> n;
    set<int> st;
    for (ll i = 0; i < n; i++)
    {
        ll num;
        cin >> num;
        st.insert(num);
    }

    if (*next(st.begin(), 1) > *next(st.begin(), 0))
        cout << *next(st.begin(), 1);
    else
        cout << "NO";
    return 0;
}