#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

long long gcd(long long a, long long b){
    while(b != 0){
        long long tmp = a % b;
        a = b;
        b = tmp;
    }
    return a;
}

int main()
{
    int n, k;
    cin >> n >> k;

    long long ret = 0;
    for(int i=1; i<n; ++i)
        ret = max(ret, gcd(i, n - i));
    cout << ret << endl;

    return 0;
}