#include<stdio.h>
void solve(int N,int K){
	long long A[N],m[2],mid,cur,used;
	int i;
	for(i=0;i<N;++i){
		scanf("%lld",&A[i]);
	}
	m[0]=0;
	m[1]=A[0]+K+1;
	while(m[1]-m[0]>1){
		mid=(m[0]+m[1])/2;
		cur=0;
		used=0;
		for(i=0;i<N;++i){
			if(A[i]+cur<mid){
				used+=(mid-cur-A[i]+i)/(i+1);
				cur+=(mid-cur-A[i]+i)/(i+1)*(i+1);
			}
		}
		m[used>K]=mid;
	}
	printf("%lld\n",m[0]);
}
int main(){
	int N,K;
	scanf("%d%d",&N,&K);
	solve(N,K);
}