#include<cstdio>
#include<cstring>
#include<iostream>
#include<cmath>
#include<ctime>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<stack>
#include<map>
using namespace std;
typedef long long LL;
const int MR=1e5+10;
int n,k;
LL a[MR];
bool check(LL x){
    LL sum=0,cnt=0;
    for(int i=1;i<=n;i++){
        if(a[i]+sum<x){
            LL t=(x-a[i]-sum+i-1)/i;
            cnt+=t;
            sum+=t*i;
        }
    }
    return cnt<=k;
}
int main(){
    cin>>n>>k;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    LL l=0,r=1e18;
    while(l+1<r){
        LL mid=(l+r)/2;
        if(check(mid)){
            l=mid;
        }
        else{
            r=mid;
        }
    }
    cout<<l<<endl;
    return 0;
}