#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000

int gcd(int a, int b) {
	if (a < b) return gcd(b, a);
	else if (b == 0) return a;
	else return gcd(b, a % b);
}

int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
	int N, K;
	cin >> N >> K;
	int ans = 1;
	REP(i, 1, N - 1) {
		ans = max(ans, gcd(N - i, i));
	}
	cout << ans << endl;



    return 0;
}