#include <stdio.h>
int main(){
	int n,v,k = 0;
	while(scanf("%d",&n) != EOF){
		float a[n];
		for(int i = 0;i < n;i++){
			scanf("%f",&a[i]);
			if(a[i] > 0)
				a[i] = a[i] / 2;
			v = v + a[i];
			if(v < 0)
				k = k + 1;
		}
		printf("%d\n",k);
		v = k = 0;	
	}
}