//#include <iostream>
//#include <string.h>
//
//using namespace std;
//#define ll long long
//#define endl '\n'
//
//const int mod = 100003;
//
//
//ll lg[21][21][21];
//ll w(ll a, ll b, ll c)
//{
//    if (a <= 0 || b <= 0 || c <= 0)
//        return 1;
//    if (a > 20 || b > 20 || c > 20)
//        return w(20, 20, 20);
//    if (lg[a][b][c])
//        return lg[a][b][c];
//    if (a < b && b < c)
//        return w(a, b, c - 1) + w(a, b - 1, c - 1) - w(a, b - 1, c);
//    return w(a - 1, b, c) + w(a - 1, b - 1, c) + w(a - 1, b, c - 1) - w(a - 1, b - 1, c - 1);
//}
//
//ll a, b, c;
//
//int main()
//{
//    ios::sync_with_stdio(false);
//    cin.tie(nullptr);
//    while (cin >> a >> b >> c)
//    {
//        if (a == -1 && b == -1 && c == -1)
//            break;
//        memset(lg, 0, sizeof lg);
//        printf("w(%lld,%lld,%lld) = %lld\n", a, b, c, w(a, b, c));
//    }
//}


#include <iostream>
#include <string.h>
#include<queue>
using namespace std;
#define ll long long
#define endl '\n'

int edge[100005], n, x, vis[100005];
struct node
{
    int step, now, to;
};
void bfs(int tar)
{
    fill(vis, vis + n, 1e9);
    queue<node>q;
    q.emplace(0, 0, edge[0]);
    vis[0] = 0;
    while (q.size())
    {
        auto [step, now, to] = q.front();
        q.pop();
        if (vis[to] >= step + 1)
        {
            q.emplace(step + 1, to, edge[to]);
            vis[to] = step + 1;
        }
        if (vis[(to + 1) % n] >= step + 2)
        {
            q.emplace(step + 1, now, (to + 1) % n);
            vis[(to + 1) % n] = step + 2;
        }
    }
    cout << vis[tar];
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    cin >> n >> x;
    for (int i = 0; i < n; i++)
    {
        int a;
        cin >> a;
        edge[i] = (i + a) % n;
    }
    bfs(x);
}