#include<stdio.h>
int main()
{
	int T;
	int m,n;
	while(scanf("%d",&T)!=EOF)
	{
		double all=0.0;
		int con=0;
		while(T--)
		{
			scanf("%d",&m);
			if(m>0)
			{
				all+=1.0*m/2;
			}else{
				all+=m;
			}
			if(all<0)
				con++;
		}
		printf("%d\n",con);
	}
}