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