#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    freopen("grupuri.in","r",stdin);
    freopen("grupuri.out","w",stdout);
    int k,n,v[100001],i,sum,j,s;
    cin>>k>>n;
    for(i=1;i<=n;i++)
        cin>>v[i];
    sum=0;
    for(i=1;i<=n-k;i++)
        sum=sum+v[i];
    if(v[n-k+1]==v[n])
        cout<<v[n]+sum/k;
    else{
        for(i=n-k+1;i<=n&&sum>0;i++){
            if(sum/(i-n+k)>v[i+1]-v[i])
                sum=sum-(i-n+k)*(v[i+1]-v[i]);
            else
                cout<<v[i]+sum/(i-n+k),sum=0;
        }
        if(sum>0)
            cout<<v[n]+sum/k;
    }
    return 0;
}