#include<stdio.h>
int main(){
	int t,a;
	while(scanf("%d",&t) != EOF){
		 int j = 0;
		 double i = 0.0;
	while(t--){
		double b;	
		scanf("%d",&a);
		if(a >= 0){
			b = a/2.0;
		}else{
			b = a;
		}
		i = i + b;
		if(i < 0){
			j++;
		}
		}
       printf("%d\n",j);
	}	
}