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