#include <bits/stdc++.h>

using namespace std;

const int N = 3e5 + ;

#define gc getchar()

int Cnt[N], tree[N], fa[N], siz[N], son[N], topp[N], deep[N], head[N];

int n, m, now = , tim;

int L[N], R[N], D[N], dis[N];

int LCA[N];

struct Node {int u, v, w, nxt;} G[N << ];

int js; 

inline int read(){

    int x = ; char c = gc;

    while(c < '' || c > '') c = gc;

    while(c >= '' && c <= '') x = x *  + c - '', c = gc;

    return x;

}

void add(int u, int v, int w){

    G[now].u = u; G[now].v = v; G[now].w = w; G[now].nxt = head[u]; head[u] = now ++;

}

void dfs_find_son(int u, int f_, int dep){

    fa[u] = f_; deep[u] = dep; siz[u] = ;

    for(int i = head[u]; ~ i; i = G[i].nxt){

        int v = G[i].v;

        if(v != f_){

            dis[v] = dis[u] + G[i].w;

            dfs_find_son(v, u, dep + );

            siz[u] += siz[v];

            if(siz[v] > siz[son[u]]) son[u] = v;

        }

    }

}

void dfs_to_un(int u, int tp){

    topp[u] = tp;

    tree[u] = ++ tim;

    if(!son[u]) return ;

    dfs_to_un(son[u], tp);

    for(int i = head[u]; ~ i; i = G[i].nxt){

        int v = G[i].v;

        if(v != son[u] && v != fa[u]) dfs_to_un(v, v);

    }

}

int Lca(int x, int y){

    int tp1 = topp[x], tp2 = topp[y];

    while(tp1 != tp2){

        if(deep[tp1] < deep[tp2]) swap(x, y), swap(tp1, tp2);

        x = fa[tp1];

        tp1 = topp[x];

    }

    return deep[x] > deep[y] ? y : x;

}

void Calc(int u){

    if(!son[u]) return ;

    for(int i = head[u]; ~ i; i = G[i].nxt){

        int v = G[i].v;

        if(v != fa[u]){

            Calc(v);

            Cnt[u] += Cnt[v];

        }

    }

}

bool See(int x){

    for(int i = ; i <= n; i ++) Cnt[i] = ;

    int B(); int Max_dis = -, Max_w = -;

    for(int i = ; i <= m; i ++)

        if(D[i] > x) Max_dis = max(Max_dis, D[i]), B ++, Cnt[L[i]] ++, Cnt[R[i]] ++, Cnt[LCA[i]] -= ;

    Calc();

    for(int i = ; i <= n; i ++) if(Cnt[i] == B) Max_w = max(Max_w, dis[i] - dis[fa[i]]);

    return Max_dis - Max_w <= x ?  : ;

}

int main()

{

    n = read(); m = read();

    int l = , r = , ans;

    for(int i = ; i <= n; i ++) head[i] = -;

    for(int i = ; i < n; i ++){

        int u = read(), v = read(), w = read();

        add(u, v, w); add(v, u, w);

    }

    dfs_find_son(, , );

    dfs_to_un(, );

    for(int i = ; i <= m; i ++){

        L[i] = read(); R[i] = read();

        LCA[i] = Lca(L[i], R[i]);

        D[i] = dis[L[i]] + dis[R[i]] - (dis[LCA[i]] * );

        r = max(r, D[i]);

    }

    while(l <= r){

        int mid = (l + r) >> ;

        if(See(mid)) ans = mid, r = mid - ;

        else l = mid + ;

    }

    printf("%d", ans);

    return ;

}

/*

6 3

1 2 3

1 6 4

3 1 7

4 3 6

3 5 5

3 6

2 5

4 5

*/