#include<stdio.h>
int main(){
       int n,a,i,d;
	   double lucky;
        while(scanf("%d",&n)!=EOF){
			lucky=0;
			d=0;
			for(i=0;i<n;i++){
				scanf("%d",&a);
				if(a<0)
					lucky+=a;
				else if(a%2==0)
					lucky+=a/2;
				else if(a%2==1)
				    lucky+=(a/2+0.5);
				
				if(lucky<0)
					d+=1;
			}
			printf("%d\n",d);
}
}