#include<stdio.h>
#include<math.h>
int main(void){
	int n,a,b,c;
	while(scanf("%d",&n)!=-1){
		b=0;
		c=0;
		while(n>0){
			scanf("%d",&a);
			if(a>=0){
				a=a/2.0;
				b=b+a;
			}
			else{
				b=b+a;
			}
			if(b<0){
				c=c+1;
			}
			n=n-1;
		}
		printf("%d\n",c);
	}
	return 0;
}