#include <bits/stdc++.h>
using namespace std;
#define modulo 1000000007
#define mod(mod_x) ((((long long)mod_x+modulo))%modulo)
#define Inf 2000000000000000000

int main(){
	
	int N,K;
	cin>>N>>K;
	long long S = 0LL;
	vector<long long> A(N);
	for(int i=0;i<N;i++){
		cin>>A[i];
		S += A[i];
	}
	
	long long ok = 0LL,ng = S+1;
	
	while(ng-ok>1){
		long long mid = (ok+ng)/2;
		vector<vector<long long>> next(17,vector<long long>(N,0LL));
		S = 0LL;
		int cnt = 0;
		int pos = 0;
		for(int i=0;i<N;i++){
			while(S<mid){
				S += A[pos];
				pos++;
				pos%=N;
				cnt++;
			}
			next[0][i] = cnt;
			cnt--;
			S -= A[i];
		}
		
		for(int i=1;i<17;i++){
			for(int j=0;j<N;j++){
				next[i][j] = next[i-1][j] + next[i-1][(j+next[i-1][j])%N];
			}
		}
		
		vector<long long> X(N,0LL);
		for(int i=0;i<17;i++){
			if((K>>i)&1){
				for(int j=0;j<N;j++){
					X[j] += next[i][(j+X[j])%N];
				}
			}
		}
		bool f = false;
		for(int i=0;i<N;i++){
			if(X[i]<=N)f=true;
		}
		if(f)ok = mid;
		else ng = mid;
	}
	
	cout<<ok<<endl;
	
	return 0;
}