#include<stdio.h>
int main(void){
	int n;
	int i,b,c;
	int a[100000];
	while(scanf("%d",&n)!=EOF){	
	    b=c=0;
	    for(i=0;i<n;i++){
			scanf("%d",&a[i]);
			if(a[i]>0)
			  a[i]=a[i]/2;
			b=b+a[i];
			if(b<0)
			c=c+1;
		}
		printf("%d\n",c);
	}
	return 0;
}