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