#include<iostream>
#include<iomanip>
#include<cmath>
#include<string>
#include<cstdlib>
#include<algorithm>

using namespace std;

int main()
{
	int n;
	int x;
	while(scanf("%d", &n)!=EOF){
		int sum = 0;
		int t = 0;
        while(n--){
        	scanf("%d", &x);
        	if(x>0){
        		x/=2;
			}
			
			sum+=x;
			if(sum<0){
				t++;
			}
		}
		
		printf("%d\n", t);
	}
	
	
	return 0;
}