#include<stdio.h>
int main(void){
	int n,a,sum=0,c=0;
	while(scanf("%d",&n)!=EOF){
		while(n--){
			scanf("%d",&a);
			if(a>0){
				sum+=a/2;}
				else{
				sum+=a;
				}
			if(sum<0)
			c+=1;
		}
		printf("%d\n",c);
		sum=0;c=0;
		}
	    return 0;
}