#include<bits/stdc++.h>
#include<string>
#include<iostream>
using namespace std;
unsigned long long a[100001];
unsigned long long f[100001];
int main()
{
	int n , m;
	cin >> n >> m;
	for(int i = 1 ;i <= n;i++)	
		cin >> a[i] ;
	for(int i = 1 ;i <= n;i++)
	{
		for(int j = 1 ;j <= m + 1;j++)
			f[i]+=a[j];
	}
	unsigned long long num = 0;
	for(int i = 1 ;i <=n;i++)
		num = max(num , f[i]);
	cout << num;
	return 0;
}