#include<bits/stdc++.h>
using namespace std;

const int maxn = 3e5 + 10;

struct edge
{
	int v, w;
	int nxt;
} e[maxn << 1];
int n, m,
ver[maxn], w[maxn], a[maxn], b[maxn], c[maxn], d[maxn], f[maxn], s[maxn], num,
top[maxn], fa[maxn], size[maxn], son[maxn], dep[maxn], dis[maxn],
l, r, mid, ans, maxw;

inline void adde(int u, int v, int w)
{
	static int ed = 1;
	e[++ed] = (edge){ v, w, ver[u] };
	ver[u] = ed;
}

inline void dfs1(int u, int f)
{
	s[++num] = u;
	size[u] = 1, fa[u] = f;
	for(int i = ver[u]; i; i = e[i].nxt)
	{
		int v = e[i].v;
		if(size[v])
			continue;
		dep[v] = dep[u] + 1;
		w[v] = e[i].w;
		dis[v] = dis[u] + w[v];
		dfs1(v, u);
		size[u] += size[v];
		if(size[son[u]] < size[v])
			son[u] = v;
	}
}

inline void dfs2(int u, int t)
{
	top[u] = t;
	if(son[u])
		dfs2(son[u], t);
	for(int i = ver[u]; i; i = e[i].nxt)
	{
		int v = e[i].v;
		if(v == fa[u] || v == son[u])
			continue;
		dfs2(v, v);
	}
}

inline int lca(int u, int v)
{
	while(top[u] != top[v])
	{
		if(dep[top[u]] < dep[top[v]])
			swap(u, v);
		u = fa[top[u]];
	}
	return dep[u] < dep[v] ? u : v;
}

inline bool check(int k)
{
	memset(f, 0, sizeof f);
	int cnt = 0;
	for(int i = 1; i <= m; i++)
	{
		if(d[i] <= k)
			continue;
		f[a[i]]++, f[b[i]]++, f[c[i]] -= 2;
		cnt++;
	}
	for(int i = n; i >= 1; i--)
	{
		f[fa[s[i]]] += f[s[i]];
		if(w[s[i]] >= maxw - k && f[s[i]] == cnt)
			return true;
	}
	return false;
}

inline int read()
{
	static int x;
	static char c;
	x = 0, c = getchar();
	while(!isdigit(c))
		c = getchar();
	while(isdigit(c))
		x = (x << 1) + (x << 3) + (c ^ 48), c = getchar();
	return x;
}

int main()
{
	n = read(), m = read();
	for(int i = 1; i < n; i++)
	{
		int u = read(), v = read(), w = read();
		adde(u, v, w);
		adde(v, u, w);
		l = max(l, w);
	}
	dep[1] = 1;
	dfs1(1, 0);
	dfs2(1, 1);
	for(int i = 1; i <= m; i++)
	{
		a[i] = read(), b[i] = read();
		c[i] = lca(a[i], b[i]);
		d[i] = dis[a[i]] + dis[b[i]] - (dis[c[i]] << 1);
		r = max(r, d[i]);
	}
	maxw = r, l = maxw - l, r++;
	while(l <= r)
	{
		mid = (l + r) >> 1;
		if(check(mid))
			ans = mid, r = mid - 1;
		else
			l = mid + 1;
	}
	printf("%d", ans);
	return 0;
}

#include <bits/stdc++.h>
#define ll long long
#define mod 1000000007
using namespace std;
const int N=300005;
struct node{
	int y,next,cost;
}b[N*2];
struct node1{
	int x,y,cost,lca;
	bool operator<(const node1 &k)const{
		return cost>k.cost;
	}
}a[N];
int n,m,k,s,t,head[N],tot,f[N][20],d[N],de[N],log2n,v[N];
int l,r,tp[N],tmp;
void add(int s,int t,int k){
	b[++tot].next=head[s];
	head[s]=tot;
	b[tot].y=t;
	b[tot].cost=k;
}
void dfs(int x,int fa){
	tp[++tmp]=x;
	for (int k=head[x];k;k=b[k].next){
		int y=b[k].y;
		if (y!=fa){
			d[y]=d[x]+b[k].cost;
			f[y][0]=x;
			de[y]=de[x]+1;
			v[y]=b[k].cost;
			dfs(y,x);
		}
	}
}
int lca(int s,int t){
	if (de[s]<de[t]) swap(s,t);
	int k=de[s]-de[t],o=0;
	while (k){
		if (k&1) s=f[s][o];
		k>>=1;++o;
	}
	if (s==t) return s;
	for (int j=log2n;j>=0;--j)
		if (f[s][j]!=f[t][j]){
			s=f[s][j];
			t=f[t][j];
		}
	return f[s][0];
}
int check(int mid){
	memset(d,0,sizeof(d));
	int sum=0;
	for (int i=1;i<=m;++i){
		if (a[i].cost>mid){//差分 
			++sum;
			d[a[i].x]++;
			d[a[i].y]++;
			d[a[i].lca]-=2;
		}
		else break;
	}
	for (int i=n;i>=1;--i)//求出每条边的权值 
		for (int k=head[tp[i]];k;k=b[k].next){
			int y=b[k].y;
			if (y!=f[tp[i]][0]) d[tp[i]]+=d[y];
		}	
	int mx=0;
	for (int i=2;i<=n;++i)
		if (d[i]==sum){//权值等于路径条数取边权最大值 
			mx=max(mx,v[i]);
		}
	if (mx>=a[1].cost-mid) return 1;
	else return 0;
}
int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	cin>>n>>m;
	for (int i=1;i<n;++i){
		cin>>s>>t>>k;
		add(s,t,k);
		add(t,s,k);
	}
	de[1]=1;
	dfs(1,0);
	log2n=log2(n);
	for (int j=1;j<=log2n;++j)
		for (int i=1;i<=n;++i)
			f[i][j]=f[f[i][j-1]][j-1];
	for (int i=1;i<=m;++i){
		cin>>a[i].x>>a[i].y;
		a[i].lca=lca(a[i].x,a[i].y);//提前求lca 
		a[i].cost=d[a[i].x]+d[a[i].y]-2*d[a[i].lca];
	}
	sort(a+1,a+1+m);//按照边权从大到小排序 
	l=0;r=0x3f3f3f3f;
	while (l<=r){//二分答案 
		int mid=(l+r)>>1;
		if (check(mid)) r=mid-1;
		else l=mid+1;
	}
	cout<<l<<endl;
}