#include <bits/stdc++.h>
#define For(i, a, b) for(int i = a; i < b; i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(int i = a; i >= b; i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
using namespace std;

using lint = long long;
using ld = long double;

int INF = 2000000000;
lint LINF = 1000000000000000000;

long long gcd(long long x, long long y) {
    if (y == 0) {
        return x;
    }
    return gcd(y, x % y);
}

int main() {
    lint n, k;
    cin >> n >> k;
    lint ans = 0;
    for (lint i = 1; i <= n - 1; i++) {
        ans = max(ans, gcd(i, n - i));
    }
    cout << ans << endl;
}