#include <stdio.h>

int main () {
	int n,i;
	int ic = 0;
	float sum = 0;
	int a[1000];
	
	while (scanf("%d",&n) != EOF) {
		for (i = 0;i < n;i++) {
			scanf("%d",&a[i]);
		}
		for (i = 0;i < n;i++) {
			if (a[i] > 0) {
				sum = sum + a[i] * 1.0 / 2;
			} else {
				sum = sum + a[i] * 1.0;
			}
			if (sum < 0) {
				ic++;
			}
		}
		printf("%d\n",ic);
		ic = 0,sum =0;
	}
	return 0;
}