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1135.cpp
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1135.cpp
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#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fr(i,j,k) for(int i=j;i<k;i++)
#define f(n) fr(i,0,n)
#define f1(n) fr(i,1,n+1)
#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
const int mod = 1e9 + 7;
vector<int>g[200005];
int pa[200005][18];
int dep[200005];
void dfs(int now, int pre) {
for (auto &i : g[now]) {
if (i == pre) {
continue;
}
dep[i] = dep[now] + 1;
pa[i][0] = now;
dfs(i, now);
}
}
int lca(int x, int y) {
if (dep[x] < dep[y]) {
swap(x, y);
}
int d = dep[x] - dep[y];
f(18) {
if (d & (1<<i)) {
x = pa[x][i];
}
}
if (x == y) {
return y;
}
for (int i = 17 ; i >= 0 ; i--) {
if (pa[x][i] != pa[y][i]) {
x = pa[x][i];
y = pa[y][i];
}
}
return pa[x][0];
}
void solve() {
int n, q;
cin >> n >> q;
fr(i,2,n+1) {
int x, y;
cin >> x >> y;
g[x].pb(y);
g[y].pb(x);
}
dfs(1, 0);
f1(17) {
fr(j,1,n+1) {
pa[j][i] = pa[pa[j][i-1]][i-1];
}
}
while(q--) {
int x, y;
cin >> x >> y;
cout << dep[x] + dep[y] - 2 * dep[lca(x, y)] << '\n';
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int c = 0;
int t;
if (!c) {
t = 1;
}
else {
cin >> t;
}
while (t--) {
solve();
}
}