#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    int n = 0,sum=0,ans=0;
    int w=0;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>w;
        sum += w;
        if(sum > 0) continue;
        ans+= 1 - sum;
        sum = 1;
    }
    cout<<ans;
    return 0;
}