#include<bits/stdc++.h>
using namespace std;
int n,m,a[3002],minn=10000,s;
int main(){
	//freopen("b.in","r",stdin);
	//freopen("b.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=3;i<=n;i++){
		s=a[i]+a[i-1]+a[i-2];
		minn=min(s,minn);
	}
	cout<<minn;
	//fclose(stdin);fclose(stdout);
	return 0;
}