#include<stdio.h>
#include<math.h>
int main(){
	int b,m,T,i;
	double a[100000],n;
	while(scanf("%d",&T)!=EOF){
		m=0;
		n=0;
		for(i=0;i<T;i++){
			scanf("%lf",&a[i]);
		}
		for(i=0;i<T;i++){
			if(fabs(a[i])==a[i])
				n+=a[i]/2;
			else
				n+=a[i];
			if(n<0)
				m++;
		}
		printf("%d\n",m);
	}
	return 0;
}