#include <stdio.h>
int main(){
	int n,i,total,x,result;
	while(scanf("%d",&n)!=EOF){
		total=0;
		result=0;
		for(i=1;i<=n;i++){
			scanf("%d",&x);
			if(x>0){
				total+=x/2;
			}
			else{
				total+=x;
			}
			if(total<0){
				result+=1;
			}
		}
		printf("%d\n",result);
	}
	return 0;
}