#include<stdio.h>
int main(){
	int n,xingyun,qiuzhang=0,i;
	float sum;
	while(scanf("%d",&n)!=EOF){
		for(i=0;i<n;++i){
			scanf("%d",&xingyun);
			if(xingyun>0){
				sum=xingyun/2.0+sum;
			}
			else{
				sum=xingyun+sum;
			}
			if(sum<0){
				qiuzhang=qiuzhang+1;
			}
		}
		printf("%d\n",qiuzhang);
		qiuzhang=0;
		sum=0;
	}
	return 0;
}