#include<bits/stdc++.h>
#define IOS ios::sync_with_stdio(), cin.tie(), cout.tie()
using namespace std;
const int N = 2e5 + 10;
long long n, m, pre[N],deg[N], dep[N], f[N][25];
vector<int> E[N];
void add(int u, int v) {E[u].push_back(v);}
void dfs(int u, int fa) {
f[u][0] = fa;
pre[u] = pre[fa] + deg[u];
dep[u] = dep[fa] + 1;
for (auto v: E[u]) {
if (v != fa) dfs(v, u);
}
}
void init() {
for (int j = 1; (1<<j) <= n; j++) {
for (int i = 1; i <= n; i++) {
f[i][j] = f[f[i][j-1]][j-1];
}
}
}
int lca(int u, int v) {
if (dep[u] < dep[v]) swap(u, v);
for (int j = 22; ~j; j--) {
if (dep[f[u][j]] >= dep[v]) u = f[u][j];
}
if (u == v) return u;
for (int j = 22; ~j; j--) {
if (f[u][j] != f[v][j]) {
u = f[u][j];
v = f[u][j];
}
}
return f[u][0];
}
int main() {
cin >> n >> m;
int u, v;
for (int i = 1; i < n; i++) {
cin >> u >> v;
add(u, v), add(v, u);
deg[u]++, deg[v]++;
}
dfs(1,0);
for (int i = 1; i <= m; i++) {
cin >> u >> v;
int k = lca(u, v);
cout << pre[u] + pre[v] - 2 * pre[k] + deg[k] << endl;
}
return 0;
}

样例过了，但测试点全wa了，求大佬看看