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