#include<stdio.h>
int main() {
	int n;
	int a, b, sum;
	while (scanf("%d", &n) != EOF)
	{
		a = b = sum = 0;
		while (n--)
		{
			scanf("%d", &a);
			if (a >= 0)
				sum += a * 1 / 2;
			if (a < 0)
				sum += a;
			if (sum < 0)
				b += 1;
		}
		printf("%d\n", b);
	}			
	return 0;
}