#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],b[MR];

bool check(LL x){
	memcpy(b,a,sizeof(a));
	LL cnt=0;
	for(int i=1;i<=n;i++){
		if(b[i]<x){
			LL t=ceil(1.0*(x-b[i])/i);
			cnt+=t;
			for(int j=i;j<=n;j++) b[j]+=t*i;
		}
	}
	return cnt<=k;
}

int main(){
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++) scanf("%lld",a+i);
    LL l=0,r=1e18;
    while(l+1<r){
        LL mid=(l+r)/2;
        if(check(mid)){
        	l=mid;
        }
        else{
        	r=mid;
        }
    }
    printf("%lld\n",l);
    return 0;
}