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


	return 0;
}