#include<stdio.h>
int main(){
	int n;
	while(scanf("%d",&n)!=EOF){
		double a[10000];
		int luck=0,q=0;
		for(int i=0;i<n;++i){
			scanf("%lf",&a[i]);
			if(a[i]>0)
			luck=luck+a[i]/2;
			else
				luck+=a[i];
			if(luck<0)
				q+=1;
		}
		printf("%d\n",q);
	}
}