#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define range(x) (x).begin(),(x).end()
const int dir[][2]={1,0,-1,0,0,1,0,-1};

const int N=100005;
int dp[N];
void solve()
{
    memset(dp,0x3f,sizeof dp);
    int n,x;
    cin>>n>>x;

    vector<int>a(n);
    for(auto& c:a)
        cin>>c;

    dp[x]=x;
    int ans=0;
    if(a[0]>x){
        ans+=n-a[0];
        a[0]=0;
    }

    for(int i=x-1;~i;--i){
        if(i+a[i]<=x)
            dp[i]=dp[i+max(a[i],1)]-i-a[i]+1;
        dp[i]+=i;
        if(i)
            dp[i]=min(dp[i],dp[i+1]);
    }

    cout<<ans+dp[0]<<'\n';
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--)
        solve();
    return 0;
}