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


}