#include<stdio.h>
int main(void){
	int n,a[1000],c,d,i;
	double b;
	while(scanf("%d",&n)!=EOF){
		b=0,d=0;
		for(i=1;i<=n;i++){
			scanf("%d",&a[i]);
		}
		for(i=1;i<=n;i++){
			if(a[i]>0)
				b=b+a[i]/2.0;
			else
				b=b+a[i];
			if(b<0)
				d=d+1;
		}
		printf("%d\n",d);
	}

}