题目链接
代码：

#include<bits/stdc++.h>
#define ll long long
inline ll mabs(ll a){
	return (a>0?a:-a);
}
using namespace std;
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	ll a,b,n;
	cin>>n>>a>>b;
	if(mabs(a-b)%2){
		cout<<min(max(a-1,b-1),max(n-a,n-b));
	}else{
		cout<<mabs(a-b)/2;
	}
	return 0;
}