#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define ll long long
#define fi first
#define se second
#define lowbit(x) (x&(-x))
const int mod=998244353;
const double eps=1e-12;
const int inf=0x3f3f3f3f;
const ll INF=0x3f3f3f3f3f3f3f3f;
#define popcnt __builtin_popcount
int dcmp(double x){if(fabs(x)<eps)return 0;return x>0?1:-1;}

#define int ll



void solve()
{
    int n;
    cin>>n;
    vector<int>a(n+1);
    for(int i=1;i<=n;i++)cin>>a[i];
    int sum=0;
    for(int i=1;i<n;i++)
    {
        sum+=a[i];
        if(sum<0)
        {
            cout<<"NO\n";
            return;
        }
    }
    cout<<"YES\n";
}

/*

*/

#undef int

int main()
{
    ios::sync_with_stdio(false);cin.tie(nullptr);
    // cout<<fixed<<setprecision(15);



    // int _;cin>>_;while(_--)
    {
        solve();
    }
    return 0;
}