#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pb push_back

#define Yes cout << "Yes\n"
#define No cout << "No\n"
#define YES cout << "YES\n"
#define NO cout << "NO\n"
#define ff first
#define ss second
#define fori(x,y) for(int i=x;i<=(int)(y);++i)
#define forj(x,y) for(int j=x;j<=(int)(y);++j)
#define fork(x,y) for(int k=x;k<=(int)(y);++k)

#define debug(x) cerr << #x << " = " << x << endl

typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

ll MOD = 998244353;
ll qpow(ll a,ll p) {ll res=1; while(p) {if (p&1) {res=res*a%MOD;} a=a*a%MOD; p>>=1;} return res;}

const int N = 2e5+7;

int arr[N];
bool vis[N];
signed main() {
	IOS;
    int n, x;
    cin >> n >> x;
    fori(0, n-1) cin >> arr[i];
    
    int ans = n;
    priority_queue<pii,vector<pii>,greater<pii>> pri;
    pri.push({0, 0});
    while (pri.size()) {
        auto pi = pri.top();
        pri.pop();
        int u = pi.second;
        if (vis[u]) continue;
        vis[u] = true;
        if (u == x) {
            ans = pi.first;
            break;
        }
        int p = (arr[u]+u)%n;
        int cnt = 0;
        while (1) {
            cnt++;
            pri.push({pi.first+cnt, p});
            // if (p == x) {
            //     ans = min(ans, pi.first+cnt);
            // }
            if (pi.first+cnt>ans) break;
            p = (p+1)%n;
        }
    }
    cout << ans << endl;
	return 0;
}