#include<stdio.h>
int main(){
	int n,a,b,q;
	double c;
	while(scanf("%d",&n)!= EOF){
		b = 0,q = 0;
	while(n--){
		scanf("%d",&a);
		if(a > 0) c = a/2;
		else c = a; 
		q = q + c;
		if(q < 0){
			b++;
		}
		}
		printf("%d\n",b);
	}
	return 0;
}