#include<bits/stdc++.h>
using namespace std;

int main()
{
	long long n,l,r,ans=0;
	cin>>n>>l>>r;
	if(r>=2*n)
	{
		ans=n-1;
	}
	else if(n<=r and r<2*n)
	{
		ans=r-n;
	}
	cout<<ans<<endl;
	return 0;
}