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