#include<iostream>
using namespace std;
using ll =long long int;
const int N=5e5+10;
ll n,m,ans=0;
ll a[N];
ll sum[N];
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        sum[i]=sum[i-1]+a[i];   
    }
    ll min_=0;
    for(int i=1;i<=n;i++){
        ans=max(ans,sum[i]-min_);
        min_=min(min_,sum[i]);
    }
    cout<<ans;
    return 0;
}