#include<stdio.h>
int main()
{
	int qiu;
	double luck;
	int n,x;
	while(scanf("%d",&n)!=EOF){
		luck=0;
		qiu=0;
		while(n--){
			scanf("%d",&x);
			if(x>=0){
				luck=luck+1.0*x/2;
			} else {
				luck=luck+x;
			}
			if(luck<0){
				qiu++;
			}
		}
		printf("%d\n",qiu);
	}
}