#include<stdio.h>
int main(){
	int i,j,k,l;
	while(scanf("%d",&i)!=EOF){
		k=0;
		l=0;
		while(i--){
			scanf("%d",&j);
			if(j>0)
			k=k+(0.5)*j;
			else
			k=j+k;
			if(k<0)
			l++;
		}
		printf("%d\n",l);
	}
	return 0;
}