/*
Author: haze
2023/12/23
13:34
*/

#include <bits/stdc++.h>

#define irep(i, l, r) for(int (i) = (l); (i) <= (r); ++(i))
#define drep(i, r, l) for(int (i) = (r); (i) >= (l); --(i))
#define ll long long
#define LL __int128
using namespace std;

inline ll read() {
    char ch = getchar();
    ll s = 0;
    bool w = 0;
    while (!isdigit(ch)) {
        if (ch == '-')w = 1;
        ch = getchar();
    }
    while (isdigit(ch))s = (s << 3) + (s << 1) + (ch ^ 48), ch = getchar();
    return w ? -s : s;
}

inline char rc() {
    char ch = getchar();
    while (1) {
        if (ch >= '!' && ch <= '~')return ch;
        ch = getchar();
    }
}

template<class T1, class T2>
T1 min(T1 AA, T2 BB) { return AA > BB ? BB : AA; }

template<class T1, class T2>
T1 max(T1 AA, T2 BB) { return AA < BB ? BB : AA; }

const int itinf = 1e9;
const ll llinf = 4e18;
const int mod = 1000000007;
const int N = 500009;

int main() {
    int n = read(), t = read();
    vector<int>a(n * 2), dis(n * 2, itinf);
    irep(i, 0, n - 1){
        a[i] = read(), a[i + n] = a[i];
    }
    dis[0] = 0;
    if(a[0] == 0){
        dis[0] = 1, a[0] = 1;
    }
    irep(i, 0, n * 2 - 1){
        if(i < n * 2 && i > a[0])dis[i] = min(dis[i], dis[i - 1] + 1);
        if(i + a[i] < 2 * n)dis[i + a[i]] = min(dis[i] + 1, dis[i + a[i]]);

    }
 //  irep(i, 0, n * 2 - 1)cerr << dis[i] <<' ';
    cout << min(dis[t], dis[t + n]);
    return 0;
}