#include <iostream>
using namespace std;

int main(){
    int n;
    cin >> n;
    int a,recruit = 0, crimes = 0;;
    for(int i = 0 ; i < n; ++ i){
        cin >> a;
        if(a > 0) recruit+=a;
        else recruit?recruit-- : crimes++;
    }
    cout<<crimes<<endl;
}