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