//Author RufatM #pragma GCC optimize("Ofast") #include <bits/stdc++.h> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> #include <ext/pb_ds/detail/standard_policies.hpp> using namespace __gnu_pbds; using namespace std; typedef long long ll; typedef pair<int,int> pii; typedef pair<ll,ll> pll; typedef vector<int> vi; typedef vector<vector<int>> vvi; typedef vector<ll> vll; typedef vector<bool> vb; typedef vector<string> vs; #define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define endl '\n' #define pb push_back #define pf push_front #define eb emplace_back #define ff first #define ss second #define all(x) begin(x),end(x) #define rall(x) rbegin(x),rend(x) #define mt19937_64 mt_rand(chrono::steady_clock::now().time_since_epoch().count()) #define ordered_set tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> const int MOD=1000000007; const int INF=1000000007; const ll LINF=4e18; const int MAXN=2005; vector<vector<vector<int>>> dp; signed main(){ fastio; #ifndef ONLINE_JUDGE //freopen("input.txt","r",stdin); //freopen("output.x","w",stdout); #endif int t=1; //cin >> t; while(t--){ int n,s,l; cin >> n >> s >> l; dp.assign(n,vvi(n,vi(n+1,0))); s--,l--; dp[s][l][n]=1; s=n-s-1; l=n-l-1; dp[s][l][n]=1; for(int z=n;z>1;z--){ for(int x=0;x<z;x++){ for(int y=0;y<z;y++){ if(x==y){ continue; } if(dp[x][y][z]==0){ continue; } for(int i=0;i<z;i++){ if(i==x){ continue; } if((i<x and (z%2==0)) or (i>=x and (z%2==1))){ continue; } int left=i-(i>x); int right=y-(y>x); dp[left][right][z-1]+=dp[x][y][z]; if(dp[left][right][z-1]>=MOD){ dp[left][right][z-1]-=MOD; } } } } } cout<<dp[0][0][1]%MOD; } }