#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5+10;
typedef long long ll;
vector<int> G[maxn];
ll n, x, y;
int depth[maxn];
int dfs(int u, int v, int p){
    int ans = 1;
    for(int i=0; i<G[u].size(); i++){
        int temp = G[u][i];
        if(temp == v) continue;
        else if(temp == p) continue;
        else {
            ans += dfs(temp, v, u);
        }
    }
    return ans;
}
bool vis[maxn];
void bfs(int u){
    memset(depth, 0, sizeof(depth));
    memset(vis, 0, sizeof(vis));
    queue<int> q;
    q.push(u);
    vis[u] = true;
    while(!q.empty()){
        int temp = q.front();
        q.pop();
        for(int i=0; i<G[temp].size(); i++){
            int v = G[temp][i];
            if(vis[v]) continue;
            else{
                depth[v] = depth[temp]+1;
                q.push(v);
                vis[v] = true;
            }
        }
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>x>>y;
    for(int i=0; i<n-1; i++){
        int u, v;
        cin>>u>>v;
        G[u].push_back(v);
        G[v].push_back(u);
    }
    ll num1 = dfs(x, y, -1);
    ll num2 = dfs(y, x, -1);
    cout<<n*(n-1)-(n-num1)*(n-num2)<<endl;
    return 0;
}