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