#include <stdio.h>

int main(){
	int n;
	while(scanf("%d", &n)!=EOF){
		double st, total, x, judg;
		st = 0;
		total = 0;
		x = 0;
		while(n--){
			scanf("%lf", &st);
			if(st>0)
				x += st/2.0;		
			else
				x += st;
			if(x<0)
			total += 1;
		}printf("%.0f\n", total);
	}
	return 0;
}