#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000

int main(){
	
	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;
}