#include<stdio.h>
int main()
{
	int i,j,n,m,k,T;
	while(scanf("%d",&n)!=EOF)
	{
		float a=0,b=0;
		for(i=0;i<n;i++)
		{
			scanf("%d",&m);
			if(m>0)a=a+m/2.0;
			else a=a+m;
			if(a<0) b=b+1;
		}
		printf("%d\n",(int)b);
	}

}