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 <iostream>
#include <vector>
#include <cstdarg>

class mystd
{
public:
    static bool Input(long long number,...);
    static bool InputArray(std::vector<long long> array);
    static bool InputArrays(long long number,...);
    static bool InputMatrix(std::vector<std::vector<long long>> array);
    static long long min(std::vector<long long> array);
    static long long max(std::vector<long long> array);
    static void print(long long number,...);
};

bool mystd::Input(long long number,...){
    va_list args;
    va_start(args, number);
    for (long long i = 0; i < number; i++)
    {
        std::cin >> *(va_arg(args, long long*));
    }
    return true;
}

void mystd::print(long long number,...){
    va_list args;
    va_start(args, number);
    for (long long i = 0; i < number; i++)
    {
        if(i!=0){
            std::cout << " ";
        }
        std::cout << *(va_arg(args, long long*));
    }
    std::cout << std::endl;;
}

bool mystd::InputArray(std::vector<long long> array){
    for (long long &i : array)
    {
        std::cin >> i;
    }
    return true;
}

bool mystd::InputArrays(long long number,...){
    va_list args;
    va_start(args, number);
    std::vector<std::vector<long long>*> arrays(number);
    for (auto &i : arrays)
    {
        i = va_arg(args, std::vector<long long>*);
    }
    long long length = arrays[0]->size();

    for (long long j=0;j<length;j++)
    {
        for (auto &&i : arrays)
        {
            std::cin >> (*i)[j];
        }
    }
    return true;
}


long long mystd::min(std::vector<long long> array){
    long long ans = array[0];
    for (long long &i : array)
    {
        if(i < ans){
            ans = i;
        }
    }
    return ans;
}


long long mystd::max(std::vector<long long> array){
    long long ans = array[0];
    for (long long &i : array)
    {
        if(i > ans){
            ans = i;
        }
    }
    return ans;
}

void Main();

int main(int argc, char const *argv[])
{
    Main();
    return 0;
}


void Main(){
    long long N,A,B,ans;
    mystd::Input(3,&N,&A,&B);
    if ((A-B)%2 == 0)
    {
        ans = B-(A+B)/2;
    } else {
        if (N-A < B-1)
        {
            ans = N-A;
        } else {
            ans = B-1;
        }
    }       

    mystd::print(1,&ans);
}