#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
#define int long long
const int N=1e5+5;
const double eps=1e-10;
const int mod=1e9+7;
#define endl '\n'
struct node{
    int first,second;
    inline bool operator<(const node &x)const{
        return second>x.second;
    }
};
void solve() {
    int n,m;
    cin>>n>>m;
    vector<int>a(n+5),vis(n+5);
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    priority_queue<node>q;
    int ans=n+5;
    int cnt=1;
    q.push({0,0});
    while(!q.empty()){
        auto y=q.top();
        q.pop();
        if(vis[y.first])continue;
        vis[y.first]=1;
        if(y.second>=ans)continue;
        int p=a[y.first];
        if((y.first+p)%n>m){
            ans=min(ans,n-((y.first+p)%n)+m+1+y.second);
        }else{
            ans=min(ans,m-((y.first+p)%n)+1+y.second);
        }
        int l=1;
        if(cnt<=500*n) {
            while ((y.first + p) % n != m) {
                q.push({(y.first + p) % n, y.second + l});
                l++;
                p++;
                p %= n;
                if (y.second + l > ans)break;
                cnt++;
            }
        }
    }
    cout<<ans<<endl;
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);cout.tie(nullptr);
    //cout<<fixed<<setprecision(12);
    int T=1;
    //  cin>>T;
    while(T--) solve();
    return 0;
}