#include<stdio.h>
int main (void){
	int n,m,i,j;
	int a[1000];
	while(scanf("%d",&n)!=EOF){
		j=0;
		m=0;
		while (n--){
			scanf("%d",&a[n]);
			if(a[n]>0){
				m+=a[n]/2;
			}
			else{
				m+=a[n];
			}
			if(m<0){
				j++;
			}
		}
		printf("%d\n",j);
	}
	return 0;
}