#include<bits/stdc++.h>
#define ull unsigned long long
#define ls(k) (k)<<1
#define rs(k) (k)<<1|1
#define debug(x) cout<<#x<<"="<<x<<endl
using namespace std;
const int inf=0x3f3f3f;
const int mod=0;
typedef pair<int,int> pii;
typedef pair<int,pii> pip;
#define _ 100005
int dis[_],vis[_];
vector<int> g[_];
void dijkstra(int x){
    memset(dis,0x3f,sizeof(dis));
    dis[x]=0;
    priority_queue<pii,vector<pii>,greater<pii>> q;
    q.push(pii(0,x));
    while(!q.empty()){
        int now=q.top().second;q.pop();
        if(vis[now]) continue;
        vis[now]=true;
        for(int to:g[now]){
            if(dis[to]>dis[now]+1){
                dis[to]=dis[now]+1;
                if(!vis[to]) q.push(pii(dis[to],to));
            }
        }
    }
}
inline void subtask(){
    int n,x;cin>>n>>x;
    int s;
    for(int i=0;i<n;i++){
        int t;cin>>t;
        g[i].push_back((i+t)%n);
        if(i) g[i-1].push_back(i);
        else s=t;
    }
    dijkstra(s);
    cout<<dis[x]+1;
}
signed main(){
    ios::sync_with_stdio(false);
    int t=1;//cin>>t;
    while(t--) subtask();
    return 0;
}