#include <cstdio>
#include <cstring>
#include <set>
using namespace std;
set<int>check[1001];
set<int>::iterator it;
int num[1000];
int main()
{
    int n;
    while(scanf("%d", &n) != EOF)
    {
        for (int i = 0 ; i <= 1000 ; i++)check[i].clear();
        for (int i = 0 ; i < n ; i++)
        {
            scanf("%d", &num[i]);
            check[num[i]].insert(i);
        }
        bool has = false;
        for (int i = 0 ; i < n ; i++)
        {
            for(int j = 0 ; j < n ; j++)
            {
                if ( i == j ) continue;
                if(num[i] - num[j] > 0)
                {
                    int x = num[i] - num[j];
                    for(it = check[x].begin() ; it != check[x].end() ; it++)
                    {
                        if( *it == i || *it == j)continue;
                        has = true;
                        break;
                    }
                }
            }
            if (has) break;
        }
        printf("%s\n",has ? ("YES") : ("NO"));
    }
    return 0;
}