#include "bits/stdc++.h"

using namespace std;
using u128 = unsigned __int128;
using u64 = unsigned long long;
using u32 = unsigned int;
using i32 = int;
using i64 = long long;
using i128 = __int128;


const i64 mod = 1e9 + 7;
const i64 inf = 1e18;

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    os << "[";
    for (int i = 0; i < v.size(); i++) {
        if (i) os << ", ";
        os << v[i];
    }
    os << "]";
    return os;
}

string to_string(i128 s) {
    if (s == 0) return "0";
    string res;
    while (s) {
        res += char(s % 10 + '0');
        s /= 10;
    }
    reverse(res.begin(), res.end());
    return res;
}

ostream &operator<<(ostream &os, i128 p) {
    os << to_string(p);
    return os;
}

#define endl '\n'


i64 qp(i64 a, i64 b) {
    i64 res = 1;
    a %= mod;
    while (b) {
        if (b & 1)
            res = res * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return res;
}

template<typename T>
void debug(T a) {
    cerr << a << endl;
}
//template<typename T, size_t size = tuple_size<T>::value>


void solve() {

    int n, m;
    cin >> n >> m;
    if (m == 0) {
        cout << 0 << endl;
        return;
    }

    vector<i64> dis(n, inf);

    vector<int> next(n, 0);

    for (int i = 0; i < n; i++) {
        cin >> next[i];
    }
    set<int> vis;
    queue<tuple<int, int>> q;
    q.push({1, next[0]});
    vis.insert(next[0]);
    while (!q.empty()) {
        auto [time, pos] = q.front();
        if (pos == m) {
            cout << time << endl;
            return;
        }
        q.pop();
        time++;
        if (!vis.count((pos + 1) % n)) {
            q.push({time, (pos + 1) % n});
            vis.insert((pos + 1) % n);
        }

        if (!vis.count((pos + next[pos]) % n)) {
            q.push({time, (pos + next[pos]) % n});
            vis.insert((pos + next[pos]) % n);
        }

    }


}

int main() {
    ios::sync_with_stdio(false), cin.tie(0);
    auto start = clock();

    int t = 1;


    while (t--) {
        solve();
    }
    auto end = clock();
    cerr << "Time: " << (double) (end - start) / CLOCKS_PER_SEC << "s" << endl;
}