#include<stdio.h>
#include<math.h>
int main(){
	int n,a,b,c;
	while(scanf("%d",&n)!=EOF){
		b=0;
		c=0;
		while(n--){
			scanf("%d",&a);
			if(a>=0)
			b=b+a/2;
			if(a<0)
			b=b+a;
			if(b<0)
			c++;
		}
		printf("%d\n",c);
	}
	return 0;
}