#include <cstdio>

#include <iostream>

#include <algorithm>

#include <queue>

#include <cmath>

#include <cstring>

#include <stack>

#include <set>

#include <map>

#include <vector>

using namespace std;

#define INF 0x7fffffff

#define LL long long

#define MAX(a,b) ((a)>(b))?

(a):(b)

struct node{

	int x,y,w;

};

int a[1000005];

LL dp[1000005];//dp[i] 为前i个里面的是包含a[i]的m个子端的最大值这里面用了滚动数组，

LL cc[1000005];//前i个分成m个子端的最大和的位置

int main(){

	int n,m;

	while(cin >> m >> n){

		for(int i = 1;i <= n;i++){

			scanf("%d",&a[i]);

			dp[i] = 0;

			cc[i] = 0;

		}

		dp[0] = 0;

		cc[0] = 0;

		LL mmax;

		for(int i = 1;i <= m;i++){

			mmax = -INF;

			for(int j = i;j <= n;j++){

				dp[j] = MAX(dp[j-1]+a[j],cc[j-1]+a[j]);

				cc[j-1] = mmax;

				mmax = MAX(mmax,dp[j]);

			}

		}

		printf("%I64d\n",mmax);

	}

	return 0;

}