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