#include <bits/stdc++.h>
using namespace std;
const int nmax = 2000;
const int Mod = 1e9 + 7;
int n,cs,cf;
long long dp[nmax + 5][nmax + 5];
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
#ifdef home
freopen("nr.in","r",stdin);
freopen("nr.out","w",stdout);
#endif // home
cin>>n>>cs>>cf;
if(cs > cf)
{
swap(cs,cf);
}
dp[0][0] = 1;
for(int i=0; i<n; i++)
{
for(int nrg=0; nrg<=i; nrg++)
{
int val = i + 1;
/// creez grup nou
if(val == cs)
{
dp[i + 1][nrg + 1] += dp[i][nrg];
dp[i + 1][nrg + 1] %= Mod;
}
else if(val == cf)
{
dp[i + 1][nrg + 1] += dp[i][nrg];
dp[i + 1][nrg + 1] %= Mod;
}
else
{
if(val < cs)
{
dp[i + 1][nrg + 1] += 1LL * dp[i][nrg] * (nrg + 1) % Mod;
dp[i + 1][nrg + 1] %= Mod;
}
else if(val < cf)
{
dp[i + 1][nrg + 1] += 1LL * dp[i][nrg] * nrg % Mod;
dp[i + 1][nrg + 1] %= Mod;
}
else if(nrg > 1)
{
dp[i + 1][nrg + 1] += 1LL * dp[i][nrg] * (nrg - 1) % Mod;
dp[i + 1][nrg + 1] %= Mod;
}
}
/// unesc doua grupuri existente
if(val != cs && val != cf && nrg > 1)
{
dp[i + 1][nrg - 1] += 1LL * dp[i][nrg] * (nrg - 1) % Mod;
dp[i + 1][nrg - 1] %= Mod;
}
/// adaug la inceput
if(val == cs)
{
dp[i + 1][nrg] += dp[i][nrg];
dp[i + 1][nrg] %= Mod;
}
/// adaug la final
if(val == cf)
{
dp[i + 1][nrg] += dp[i][nrg];
dp[i + 1][nrg] %= Mod;
}
}
}
cout<<dp[n][1]<<'\n';
return 0;
}
