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