#include <bits/stdc++.h>
using namespace std;
int main(){
	int n , m , minn = 1e9;
	scanf("%d %d" , &n , &m);
	int a[n + 1];
	for(int i = 1 ; i <= n ; i++){
		scanf("%d" , &a[i]);
	}
	for(int i = 1 ; i <= n - 3 ; i++){
		if(a[i] + a[i + 1] + a[i + 2] < minn){
			minn = a[i] + a[i + 1] + a[i + 2];
		}
	}
	printf("%d" , minn);
	return 0;
}