#include<stdio.h>
int main(){
	int n,a,sp=0,i;float luck=0;
	while(scanf("%d",&n)!=EOF){
		for(i=1;i<=n;i++){
			scanf("%d",&a);
			if(a>0){
				luck=luck+a*1.0/2;
			}else{
				luck=luck+a;
			}
			if(luck<0){
				sp++;
			}
		}
		printf("%d\n",sp);
		sp=0;luck=0;
	}
}