#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long ll;

const double EPS = 1e-8;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

int main(void) {
	int n,k;
	cin >> n >> k;
	int ans = 0;
	for(int i=1;i<n;i++){
		ans = max(ans,__gcd(i,n-i));
	}

	cout << ans << endl;
	return 0;
}