#include<stdio.h>
int main(){
	int n,i,s,a[1000000],m;
	while(scanf("%d",&n)!=EOF){
		s=0;m=0;
		for(i=0;i<n;i++){
		scanf("%d",&a[i]);
			if(a[i]<0)
				m=m+a[i];
			else if(a[i]>=0)
			m=m+a[i]/2;
			if(m<0)
				s++;
		}
		printf("%d\n",s);

	}
	return 0;
}