#pragma GCC optimize("Ofast,unroll-loops,O3") #include <bits/stdc++.h> using namespace std; #ifdef LOCAL #include "algo/debug.h" #else #define debug(...) 73 #endif using int64 = int64_t; using ld = long double; using uint64 = uint64_t; using int128 = __int128_t; #define all(v) (v).begin(), (v).end() #define rall(v) (v).rbegin(), (v).rend() const int md = 1e9 + 7; const int64 inf = 1e18; int mul(int x) { return (x + md) % md; } int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); int n, cs, cf; cin >> n >> cs >> cf; vector<vector<vector<vector<int>>>> dp(n + 1, vector<vector<vector<int>>>(n + 1, vector<vector<int>>(n + 1, vector<int>(2, 0)))); for (int i = 2; i <= n; i++) { for (int s = 1; s < i; s++) { for (int f = s + 1; f <= i; f++) { for (int w = 0; w < n; w++) { for (int k = 1; k <= i; k++) { dp[i][s][f][w] = mul(dp[i - 1][k][f - (f > s)][(w == 1 ? 0 : 1)] + dp[i][s][f][w]); } } } } } cout << mul(dp[n][cs][cf][0] + dp[n][cs][cf][1]) << '\n'; return 0; }