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