#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()

using namespace std;
using ll = long long;
vector<vector<int>> g;
vector<bool> used;

void Dfs(int from) {
    used[from] = true;
    for (int to : g[from]) {
        if (!used[to]) {
            Dfs(to);
        }
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, t;
    cin >> n >> t;
    g.resize(n);
    used.assign(n, false);
    for (int i = 0; i < n - 1; i++) {
        int from = i;
        int a;
        cin >> a;
        int to = i + a;
        g[from].push_back(to);
    }
    Dfs(0);
    if (used[t - 1] == true) {
        cout << "YES\n";
    } else {
        cout << "NO\n";
    }
}