#include<cstdio>

#include<algorithm>

#include<cmath>

#include<cstring>

#define maxn 600500

#define ll long long

using namespace std;

struct st{

    ll u,v,next,val;

}s[maxn];

struct qu{

    ll a,b,lca,len;

}quest[maxn];

ll n,m,u,v,root,tot,val,head[maxn],ceng[maxn],fa[maxn][],len[maxn],fedge[maxn],zou[maxn],cf[maxn],maxlen,l,r,ma;

inline void add(ll u,ll v,ll val)

{

    tot++;

    s[tot].val = val;

    s[tot].u = u;

    s[tot].v = v;

    s[tot].next = head[u];

    head[u] = tot;

}

inline void dfs(ll f,ll now)

{

    fa[now][] = f;

    ceng[now] = ceng[f] + ;

    for(ll i = head[now];i;i = s[i].next)

    {

        v = s[i].v;

        if(!ceng[v])

        {

            fedge[v] = s[i].val;

            len[v] = len[now] + s[i].val;

            dfs(now,v);

        }

    }

}

inline void init()

{

    for(ll j=;(<<j)<=n;j++)

    {

        for(ll i=;i<=n;i++)

        {

            fa[i][j]=fa[fa[i][j-]][j-];

        }

    }

}

inline ll lca(ll a,ll b)

{

    if(ceng[a] > ceng[b]) swap(a,b);

    ll cha = ceng[b] - ceng[a];

    for(ll i = ;( << i) <= cha;i++)

    {

        if(( << i) & cha) b = fa[b][i];

    }

    if(a!=b)

    {

        for(ll i=(ll)log2(n);i>=;i--)

        {

            if(fa[a][i]!=fa[b][i])

            {

                a=fa[a][i];

                b=fa[b][i];

            }

        }

        a = fa[a][];

    }

    return a;

}

inline ll find(ll pos,ll num)

{

    ll val = cf[pos];

    zou[pos] = ;

    for(ll i=head[pos];i;i=s[i].next)

    {

        if(zou[s[i].v]) continue;

        val += find(s[i].v,num);

    }

    if(val >= num) ma = max(ma,fedge[pos]);

    return val;

}

inline ll check(ll ans)

{

    memset(zou,,sizeof(zou));

    memset(cf,,sizeof(cf));

    ll ce = ;

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

    {

        if(quest[i].len > ans)

        {

            cf[quest[i].a]++;

            cf[quest[i].b]++;

            cf[quest[i].lca] -= ;

            ce++;

        }

    }

    ma = -;

    find(,ce);

    if(ma == -) return ;

    if(ans + ma >= maxlen) return ;

    return ;

}

int main(){

    scanf("%lld%lld%",&n,&m);

    for(ll i=;i<n;i++)

    {

        scanf("%lld%lld%lld",&u,&v,&val);

        add(u,v,val);

        add(v,u,val);

    }

    dfs(,);

    init();

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

    {

        scanf("%lld%lld",&u,&v);

        quest[i].a = u;

        quest[i].b = v;

        quest[i].lca = lca(u,v);

        quest[i].len = len[u] + len[v] -  * len[quest[i].lca];

        maxlen = max(maxlen , quest[i].len);

    }

    r = maxlen;

    while(l < r)

    {

        ll mid = l + r >> ;

        if(check(mid)) r = mid;

        else l = mid + ;

    }

    printf("%lld",l);

} 

#include<cstdio>

#include<algorithm>

#define maxn 300300 << 1

using namespace std;

int head_edge[maxn],head_quest[maxn],fedge[maxn],f[maxn],len[maxn],vis[maxn],cf[maxn],n,m,ma,maxlen,tot,u,v,val,l,r;

struct st{

    int v,val,next;

}s[maxn];

struct que{

    int u,v,lca,len,next;

    que *es;

}quest[maxn];

inline int find(int x)

{

    if(f[x] == x) return x;

    f[x] = find(f[x]);

    return f[x];

}

inline void add_edge(int u,int v,int val)

{

    tot++;

    s[tot].v = v;

    s[tot].val = val;

    s[tot].next = head_edge[u];

    head_edge[u] = tot;

}

inline void add_quest(int u,int v)

{

    tot++;

    quest[tot].u = u;

    quest[tot].v = v;

    if(tot & )    quest[tot].es = &quest[tot + ];

    else quest[tot].es = &quest[tot - ];

    quest[tot].next = head_quest[u];

    head_quest[u] = tot;

}

inline void dfs_tarjan(int father,int now)

{

    for(int i=head_edge[now];i;i=s[i].next)

    {

        if(father == s[i].v) continue;

        fedge[s[i].v] = s[i].val;

        len[s[i].v] = len[now] + s[i].val;

        dfs_tarjan(now,s[i].v);

    }

}

inline void lca_tarjan(int father,int now)

{

    for(int i=head_edge[now];i;i=s[i].next)

    {

        if(s[i].v == father) continue;

        lca_tarjan(now,s[i].v);

    }

    for(int i=head_quest[now];i;i=quest[i].next)

    {

        if(vis[quest[i].v])

        {

            quest[i].lca = find(quest[i].v);

            quest[i].len = len[quest[i].u] + len[quest[i].v] -  * len[quest[i].lca];

            quest[i].es -> lca = quest[i].lca;

            quest[i].es -> len = quest[i].len;

            maxlen = max(maxlen,quest[i].len);

        }

    }

    vis[now] = ;

    f[now] = father;

}

inline int dfs_check(int pos,int num)

{

    vis[pos] = ;

    int val = cf[pos];

    for(int i=head_edge[pos];i;i=s[i].next)

    {

        if(vis[s[i].v]) continue;

        val += dfs_check(s[i].v,num);

    }

    if(val >= num) ma = max(ma,fedge[pos]);

    return val;

}

inline int check(int ans)

{

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

    {

        vis[i] = ;

        cf[i] = ;

    }

    int num = ;

    ma = -;

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

    {

        if(quest[i].len > ans)

        {

            cf[quest[i].u]++;

            cf[quest[i].v]++;

            cf[quest[i].lca] -= ;

            num++;

        }

    }

    if(!num) return ;

    dfs_check(,num);

    if(ma == - || ans + ma < maxlen) return ;

    return ;

}

int main(){

    scanf("%d%d",&n,&m);

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

    {

        scanf("%d%d%d",&u,&v,&val);

        add_edge(u,v,val);

        add_edge(v,u,val);

    }

    dfs_tarjan(,);

    tot = ;

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

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

    {

        scanf("%d%d",&u,&v);

        add_quest(u,v);

        add_quest(v,u);

    }

    lca_tarjan(,);

    for(int i=;i<=m;i++) quest[i] = quest[i * ];

    r = maxlen;

    l = max(,r - );

    while(l < r)

    {

        int mid = l + r >> ;

        if(check(mid)) r = mid;

        else l = mid + ;

    }

    printf("%d",l);

}