#include<stdio.h>
int main(){
	int n,m;
	while(~scanf("%d",&n)){
		double total1=0;
		int total2=0;
		for(int i=0;i<n;i++){
			scanf("%d",&m);
			if(m>=0)
			total1+=(m/2.0);
			else total1+=m;
			if(total1<0)
			total2++;
		}
		printf("%d\n",total2);
	}
	return 0;
}