#include <bits/stdc++.h>
#define pb push_back
using namespace std;
const int N = 5e4 + 5;
int n, a, b, k, x, y, lg[30], ans, cnt[N], fa[N][30], dep[N], vis[N];
map <pair<int, int>, int> mp;
vector <int> v[N];

inline void dfs(int now){   
    for (int i = 0; i < v[now].size(); ++i){
        int nx = v[now][i]; 
        if (fa[now][0] != nx){
            fa[nx][0] = now;
            dep[nx] = dep[now] + 1;
            dfs(nx);
        }
    }
}

inline void dfs2(int x, int last){
    for (int i = 0; i < v[x].size(); ++i){
        int nx = v[x][i];
        if (nx == last) continue;
        dfs2(nx, x);
        cnt[x] += cnt[nx];
    }
    ans = max(cnt[x], ans);
}

inline int lca(int x, int y){
    if (dep[x] < dep[y]) swap(x, y);
    for (int i = lg[dep[x] - dep[y]]; i >= 0; --i){
        if (dep[x] - dep[y] >> i & 1) x = fa[x][i];
    }

    if (x == y) return x;
    for (int i = lg[dep[x]]; i >= 0; --i){
        if (fa[x][i] != fa[y][i]) x = fa[x][i], y = fa[y][i];
    }

    return fa[x][0];
}
int main(){
    scanf("%d%d", &n, &k);
    for (int i = 1; i < n; ++i){
        scanf("%d%d", &a, &b);
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs(1);
    for (int i = 1; i <= n; ++i) lg[i] = lg[i - 1] + (1 << lg[i - 1] + 1 == i);
    for (int i = 1; i <= lg[n]; ++i){
        for (int j = 1; j <= n; ++j){
            fa[j][i] = fa[fa[j][i - 1]][i - 1];
        }
    }

    for (int i = 1; i <= k; ++i){
        scanf("%d%d", &a, &b);
        cnt[a] ++, cnt[b] ++;
        int c = lca(a, b);
        cnt[c] --;
        cnt[fa[c][0]] --;
    }
    dfs2(1, 0);
    printf("%d\n", ans);
    return 0;
}