#include<stdio.h>
int main(){
	int n;
	while(scanf("%d",&n)!=EOF){
		double xingyunzhi=0,x;
		int qiuzhangzhi=0;
	    while (n--){
			scanf("%lf",&x);
			if(x>0){
				xingyunzhi=xingyunzhi+x/2;
			}
			if(x<=0){
				xingyunzhi=xingyunzhi+x;
			}
			if(xingyunzhi<0){
				qiuzhangzhi++;
			}
		
		}
		printf("%d\n",qiuzhangzhi);
	}
	return 0;
}