#include<stdio.h>

int main(){
	int n, a, count;
	double b, s;
	while(scanf("%d", &n) != EOF){
		count = 0;
		s = 0;
		b = 0;
		while(n--){
			scanf("%d", &a);
			if(a > 0){
				b = a*1.0 / 2;
				s = s + b;
			}else{
				s = s + a;
			}
			if(s < 0){
				count++;
			}
		}
		printf("%d\n", count);
	}
	return 0;
}