#include <algorithm>
#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const long long PIN=4557430888798830399;
const int N=75;
struct Edge{
	int u,v;
};
Edge edge[N];
bool in_tree[N],ban[N],bj[N];
int n,m,fa[N],cnt[N],fr[N];
int len_list=0,e[N],ne[N],h[N];
long long a[N],b[N],c[N],d[N];
void add_once(int a,int b){
	e[len_list]=b;
	ne[len_list]=h[a];
	h[a]=len_list;
	len_list++,cnt[a]++;
}
bool cmp(int u,int v){
	if((c[u]<d[u])!=(c[v]<d[v])) return c[u]<d[u];
	if(c[u]<d[u]) return c[u]<c[v];
	return d[u]>d[v];
}
void dfs(int u,int from){
	fr[u]=from;
	for(int i=h[u];i>=0;i=ne[i])
		dfs(e[i],i);
}
struct Heap{
	int n,a[N],p[N];
	void up(int u){
		while(u>1&&cmp(a[u],a[u/2])){
			swap(p[a[u]],p[a[u/2]]);
			swap(a[u],a[u/2]); u/=2;
		}
	}
	void down(int u){
		while(u*2<=n&&cmp(a[u*2],a[u])||u*2<n&&cmp(a[u*2+1],a[u]))
			if(u*2==n||cmp(a[u*2],a[u*2+1])){
				swap(p[a[u]],p[a[u*2]]);
				swap(a[u],a[u*2]); u*=2;
			}
			else{
				swap(p[a[u]],p[a[u*2+1]]);
				swap(a[u],a[u*2+1]); u=u*2+1;
			}
	}
	void push(int x){
		a[++n]=x; p[x]=n; up(n);
	}
	void pop(){
		if(n==1){
			p[a[1]]=0;
			n=0; return ;
		}
		p[a[1]]=0,p[a[n]]=1;
		a[1]=a[n--]; down(1);
	}
	void erase(int x){
		if(n==1){
			p[a[1]]=0;
			n=0; return ;
		}
		p[a[n]]=p[x]; a[p[x]]=a[n--];
		up(p[x]),down(p[x]); p[x]=0;
	}
	bool empty(){
		return n==0;
	}
	int top(){
		return a[1];
	}
};
Heap hp;
int merge(int u){
	int v=fa[u],i,la;
	long long nd=d[u]-c[u]+d[v]-c[v];
	long long na=max(c[v],c[v]-d[v]+c[u]);
	long long nb=na+nd;
	if(cnt[u]>cnt[v]){
		for(i=h[v],la=-1;i>=0;i=ne[i])
			if(e[i]==u)
				if(la==-1) h[v]=ne[i];
				else ne[la]=ne[i];
			else fa[e[i]]=u,la=i;
		fa[u]=fa[v],fr[u]=fr[v],e[fr[v]]=u;
		if(la>=0) ne[la]=h[u],h[u]=h[v],h[v]=-1;
		ban[v]=1,cnt[u]+=cnt[v],cnt[v]=0;
		c[u]=na,d[u]=nb;
		return u;
	}
	else{
		for(i=h[u],la=-1;i>=0;i=ne[i])
			fa[e[i]]=v,la=i;
		if(la>=0) ne[la]=h[v],h[v]=h[u],h[u]=-1;
		ban[u]=1,cnt[v]+=cnt[u],cnt[u]=0;
		c[v]=na,d[v]=nb;
		return v;
	}
}
long long solve(){
	int i,s1; len_list=0;
	long long ans=0,sum=0;
	memset(h,-1,sizeof h);
	memset(ban,0,sizeof ban);
	memset(cnt,0,sizeof cnt);
	for(i=1;i<=m;i++){
		if(!in_tree[i]) continue;
		fa[edge[i].v]=edge[i].u;
		add_once(edge[i].u,edge[i].v);
	}
	dfs(1,-1);
	for(i=1;i<=n;i++)
		c[i]=a[i],d[i]=b[i];
	for(i=2;i<=n;i++) hp.push(i);
	while(!hp.empty()){
		s1=hp.top(),hp.pop();
		if(fa[s1]==1) continue;
		if(!cmp(s1,fa[s1])) continue;
		hp.erase(fa[s1]);
		hp.push(merge(s1));
	}
	hp.push(1);
	while(!hp.empty()){
		s1=hp.top(),hp.pop();
		ans=min(ans,sum-c[s1]);
		sum=sum-c[s1]+d[s1];
		for(i=h[s1];i>=0;i=ne[i])
			if(!ban[e[i]]) hp.push(e[i]);
	}
	return -ans;
}
bool sort_cmp(const Edge& a,const Edge& b){
	if(a.u!=b.u) return a.u<b.u;
	return a.v<b.v;
}
long long get_tree(int u,int cnt){
	if(u+(n-1-cnt)-1>m) return PIN;
	if(u>m) return solve();
	if(bj[edge[u].v]) return get_tree(u+1,cnt);
	in_tree[u]=bj[edge[u].v]=1;
	long long ans=get_tree(u+1,cnt+1);
	in_tree[u]=bj[edge[u].v]=0;
	return min(ans,get_tree(u+1,cnt));
}
int main(){
//	freopen("HP.in","r",stdin);
//	freopen("HP.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i=2;i<=n;i++)
		scanf("%lld%lld",&a[i],&b[i]);
	for(int i=1;i<=m;i++)
		scanf("%d%d",&edge[i].u,&edge[i].v);
	sort(edge+1,edge+m+1,sort_cmp);
	printf("%lld",get_tree(1,0));
//	fclose(stdin);
//	fclose(stdout);
	return 0;
}