#include<iostream>
using namespace std;
int main()
{
	int a,b,x,r,y,s=0,n=0;
	cin>>a>>b;
	for(x=a;x<=b;x++)
	{
		r=0;
		y=x;
		while(y>0)
		{
			r=r*10+y%10;
			y=y/10;
		}
		if(r==x)
		{
			s=s+x;
			n++;
		}
	}
	if(n==0) cout<<"nu exista palindroame";
        else cout<<(float)s/n;
	return 0;
}