#include<bits/stdc++.h>
using namespace std;
ifstream f("grupuri.in");
ofstream g("grupuri.out");
long long n,k,v[100002],ad,nr,s[100002];
int main()
{
    f>>k>>n;
    for(long long i=1;i<=n-k;++i)
        f>>nr,ad+=nr;
    for(long long i=1;i<=k;++i)
        f>>v[i],s[i]=v[i]+s[i-1];
    long long sol=0;
    if(ad>=v[k]*k-s[k]){
        ad=ad-v[k]*k+s[k];
        sol=v[k]+ad/k;
        g<<sol<<'\n';
    }
    else
        for(int i=2;i<=k;++i)
            if(v[i]*i-s[i]<=ad && v[i+1]*(i+1)-s[i+1]>ad){
                g<<v[i]<<" ";
                return 0;
            }
    return 0;
}