#include<stdio.h>


int main(){
	int t,l,s,b;
	
	while(scanf("%d",&t)!=EOF){
		l=0;
		s=0;
		while(t--){
			scanf("%d",&b);
			if(b>0){
				b=b/2.0;
			}
			s+=b;
			if(s<0){
				l+=1;
			}
		}
		printf("%d\n",l);
		
		
	}
	
	return 0;
}