#include<bits/stdc++.h>
using namespace std;
int main()
{
	int x,y,z,n=0;
	cin>>x>>y>>z;
	if(y-z>z-y){
		for(;z-x&&z-x;){
			x=y+1;
			y=x+1;
			n++;
		}
	}
	else{
		for(;z-x&&z-x;){
			z=y-1;
			y=z-1;
			n++;
		}
	}
	cout<<n;
	return 0;
}

20分