从前扫到后，计算前缀和，维护前缀和最小值，打完收工。

#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 50004;
#define ll long long 
ll a[maxn],n,ans;
int main()
{
   // freopen("in.txt","r",stdin);
    scanf("%lld",&n);
    for(int i = 1; i<=n; i++){
        scanf("%lld",&a[i]);
        ans=min(ans,a[i]=a[i]+a[i-1]);
    }
    printf("%lld\n",-ans);
    return 0;
}