#include <iostream>
using namespace std;

template <typename T>
T gcd(T a, T b){
	while(b){
		T tmp = b;
		b = a % b;
		a = tmp;
	}
	return a;
}

int main(){
	int64_t n, k;
	cin >> n >> k;
	int64_t ans = 1;
	for(int64_t i = 1; i < n; i++) ans = max(ans, gcd(i, n - i));
	cout << ans << endl;
}