#include <iostream>
#include <map>
#include <unordered_map>
#include <set>
#define ll long long
using namespace std;
ll n, x;
const ll mxn = 1e5 + 5;
ll arr[mxn];
set <ll> v;
const ll INF = 1e9;
ll solve(ll i, ll j)
{
    if (i == j)
    {
        v.insert(i * n + j);
        return 0;
    }
    else
    {
        ll idx_1 = ((i + arr[i] + 1) % n) * n + j;
        ll idx_2 = ((i + arr[i]) % n) * n + j;
        ll ans_1, ans_2;
        v.insert(i * n + j);
        if (v.find(idx_1) == v.end())
        {
            ans_1 = solve((i + arr[i] + 1) % n, j) + 2;
        }
        else
        {
            ans_1 = INF;
            //v.insert(idx_1);
        }
        if (v.find(idx_2) == v.end())
        {
            ans_2 = solve((i + arr[i]) % n, j);
        }
        else
        {
            ans_2 = INF;
            //v.insert(idx_2);
        }
        //ll ans = INF;
        ll ans_3 = j - arr[i] + 1;
        return min(min(ans_1, ans_3),ans_2);
    }
}
int main()
{
    cin >> n >> x;
    for (ll i = 0 ; i < n ; i++)
    {
        cin >> arr[i];
    }
    ll ans = 0;
    ans = solve(0, x);
    cout << ans << "\n";
}