#include<stdio.h>
#include<math.h>

int main(){
	int n;
	while(scanf("%d",&n) != EOF){
		float luck = 0;
		int sum = 0,step;
		while(n--){
			scanf("%d",&step);
			if(step > 0){
				luck = luck + step*1.0/2.0;
			}else {
				luck = luck + step;
			}
			if(luck < 0){
				sum = sum + 1;
			}
		}
		printf("%d\n",sum);
	}
	return 0;
}