#include <iostream>
#include <algorithm>
using namespace std;

const int MAX_N = 200000;
int N, ct;
int A[MAX_N];

int main() {
    cin >> N;
    for (int i = 0; i < N; i++)
        cin >> A[i];
    ct = 1;
    for (int i = 0; i < N; i++) {
        if (A[i] <= abs(ct))
            ct = ((ct + 1 == 0) ? 1 : ct + 1);
        else if (ct > 0)
            ct -= A[i];
        else
            ct = -A[i] + 1;
    }
    cout << ((ct < 0) ? "No" : "Yes") << endl;
    return 0;
}