#include<stdio.h>
int main() {
	int n,m,s,a;
	while(scanf("%d",&n)!=EOF) {
		s = 0,a = 0;
		while(n--) {
			scanf("%d",&m);
			s += m>0?m/2:m;
			a += s<0?1:0;
		}
		printf("%d\n",a);
	}
}