Problem:
Score : 300 points

Problem Statement

2N players are running a competitive table tennis training on N tables numbered from 1 to N.

The training consists of rounds.
In each round, the players form N pairs, one pair per table.
In each pair, competitors play a match against each other.
As a result, one of them wins and the other one loses.

The winner of the match on table X plays on table X-1 in the next round,
except for the winner of the match on table 1 who stays at table 1.

Similarly, the loser of the match on table X plays on table X+1 in the next round,
except for the loser of the match on table N who stays at table N.

Two friends are playing their first round matches on distinct tables A and B.
Let's assume that the friends are strong enough to win or lose any match at will.
What is the smallest number of rounds after which the friends can get to play a match against each other?

Constraints

2 \leq N \leq 10^{18}

1 \leq A < B \leq N

All input values are integers.

Input

Input is given from Standard Input in the following format:

N A B

Output

Print the smallest number of rounds after which the friends can get to play a match against each other.

Sample Input 1

5 2 4

Sample Output 1

1

If the first friend loses their match and the second friend wins their match, they will both move to table 3 and play each other in the next round.

Sample Input 2

5 2 3

Sample Output 2

2

If both friends win two matches in a row, they will both move to table 1.

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
#define int             long long int
#define pb              push_back
#define se              second
#define mp              make_pair
#define fi              first
#define del(a,vec)      vec.erase(std::remove(vec.begin(), vec.end(), a), vec.end());
#define search(f,l,v)   binary_search(f,l,v)
#define iter(a,b)       vector<int>::iterator a,b
#define lower(v,num)    lower_bound (v.begin(), v.end(), num);
#define upper(v,num)    upper_bound (v.begin(), v.end(), num); 
#define removecopy(a)   unique(a.begin(), a.end()); 
#define vi              vector<int> 
#define pi              pair<int,int>    
#define vpi             vector<pi>      
#define mlbb            ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)    
int mod =1000000007;
namespace Rahul{
    bool isPrime(int n) 
    {if (n <= 1)  return false; if (n <= 3)  return true; 
    if (n%2 == 0 || n%3 == 0) return false; 
    for (int i=5; i*i<=n; i=i+6) 
        if (n%i == 0 || n%(i+2) == 0) 
           return false; 
    return true; }
    int pow (int x, int n,int mod) {//calculate x^n
    if (n == 0) return 1;
 
    int res = pow (x, n / 2,mod);
 
    res = (res * res) % mod;
    if (n % 2) res = (res * x ) % mod;
 
    return res;
    }
    int _gcd(int a,int b)
    {
        if(a==0)
            return b;
        else    
            return _gcd(b%a,a);
    }
    //s.erase(s.find(2)) where s={1,2,3,3,2}; 
};
using namespace Rahul;
int32_t main()
{
    mlbb;
    int n,a,b;
    cin>>n>>a>>b;
    int a1= min(a,b);
    int a2=max(a,b);
    a=a1;
    b=a2;
    
    
   
        if((b-a)%2) {
            if(a==1 || b==n)
            {
                int ans= 1+ (b-a)/2;
                ans = min(ans , b-1);
                ans  = min(ans, n-a);
                cout<<ans<<endl;
            }
            else
            {
                int ans= min(n-a, b-1);
                cout<<ans<<endl;
            }
            
        }
        else cout<<(b-a)/2<<endl;
    // }
    
}