#include <cmath>
#include <stack>
#include <vector>
#include <iostream>
using namespace std;
const int N = 5005;
int primes[N], cnt;
int sum[N];
bool st[N];
void get_primes(int n){
for(int i = 2; i <= n; i++){
if(!st[i]) primes[cnt++] = i;
for(int j = 0; primes[j] <= n / i; j++){
st[primes[j] * i] = 1;
if(i % primes[j] == 0) break;
}
}
}
int get(int n, int p){
int res = 0;
while(n){
res += n / p;
n /= p;
}
return res;
}
vector<int> mul(vector<int> a, int b){
vector<int> c;
int t = 0;
for(int i = 0; i < a.size(); i++){
t += a[i] * b;
c.push_back(t % 10);
t /= 10;
}
while(t){
c.push_back(t % 10);
t /= 10;
}
return c;
}
int main() {
int a, b;
cin >> a >> b;
get_primes(a);
for(int i = 0; i < cnt; i++){
int p = primes[i];
sum[i] = get(a, p) - get(b, p) - get(a - b, p);
}
vector<int> res;
res.push_back(1);
for(int i = 0; i < cnt; i++){
for(int j = 0; j < sum[i]; j++){
res = mul(res, primes[i]);
}
}
for(int i = res.size() - 1; i >= 0; i--){
cout << res[i];
}
return 0;
}
