#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, cs, cf;
cin >> n >> cs >> cf;
vector<vector<int>> dp(n+1, vector<int>(n+1, 0));
dp[1][1] = 1;
for(int i=2;i<=n;i++) {
for(int j=i;j>=1;j--) {
if(i==cs || i==cf) {
// first ya last component k begin/end me respectively ghus jao
dp[i][j] += dp[i-1][j];
// ya fir first ya last me apna hi component bana lo
dp[i][j] += dp[i-1][j-1];
}
else {
// kinhi do component ke bich me ghuske unko merge kr do
dp[i][j-1] += dp[i-1][j] * (j-1);
// kinhi do componenet ke bich apna ek naya component bana lo
// starting ke pehle aur ending ke baad nahi ja skte
dp[i][j] += dp[i-1][j-1] * (j - (i>cs) - (i>cf));
}
}
}
cout << dp[n][1] << endl;
// for(int i=1;i<=n;i++) {
// for(int j=1;j<=n;j++) {
// cout << dp[i][j] << " ";
// }
// cout << endl;
// }
return 0;
}
