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