ll@n,c=0,d=0,e=0;
rep(n){
	ll@a,@b;
	if(a%8==0){
		c+=b;
	}else if(a%4==0){
		d+=b;
	}else if(a%2==0){
		e+=b;
	}
}
wt(c+(d>=e?e+(d-e)/2:d+(e-d)/3));