#include<bits/stdc++.h>
using namespace std;
#define int long long
const int INF=1e18;
int n,m;
vector<int>edge[105];
vector<int>fedge[105];
int x[105],y[105];
int bx[105],by[105];
int cnt[105];
int dp[70000005];
int ret=INF;
int solve1(){
	dp[1]=0;
	for(int i=2;i<(1ll<<n);i++) dp[i]=INF;
	int sum=0;
	for(int i=1;i<(1ll<<n);i++){
		for(int j=0;j<n;j++){
			if(((i>>j)&1)&&(!(((i-1)>>j)&1))){
				sum+=y[j+1]-x[j+1];
				for(int k=0;k<edge[j+1].size();k++) cnt[edge[j+1][k]]++;
			}
			else if((((i-1)>>j)&1)&&(!((i>>j)&1))){
				sum-=y[j+1]-x[j+1];
				for(int k=0;k<edge[j+1].size();k++) cnt[edge[j+1][k]]--;
			}
			else break;
		}
		for(int j=1;j<=n;j++) if(cnt[j]&&(!((i>>(j-1))&1))) dp[i^(1<<(j-1))]=min(dp[i^(1<<(j-1))],dp[i]+max(0ll,x[j]-dp[i]-sum));
	}
	return dp[(1ll<<n)-1];
}
struct node{
	int x,y,id;
    bool operator < (const node& ano) const {
    	if(y>=0&&ano.y<0) return 1;
		else if(y<0&&ano.y>=0) return 0;
		else if(y>=0){
			if(x!=ano.x) return x<ano.x;
			else if(y!=ano.y) return y<ano.y;
			else return id<ano.id;
		}
		else{
			if(x+y!=ano.x+ano.y) return x+y>ano.x+ano.y;
			else if(x!=ano.x) return x<ano.x;
			else if(y!=ano.y) return y<ano.y;
			else return id<ano.id;
		}
    }
};
int fa[105],f[105];
int find(int x){
	if(fa[x]==x) return x;
	fa[x]=find(fa[x]);
	return fa[x];
}
void merge(int a,int b){
	x[a]=max(x[a],x[b]-y[a]);
	y[a]+=y[b];
}
bool vis[105];
vector<int>tmp[105];
bool check(int x){
	vis[x]=1;
	int ret=1;
	for(int i=0;i<tmp[x].size();i++){
		int v=edge[x][i];
		if(vis[v]) return 0;
		ret&=check(v);
	}
	return ret;
}
int calc(){
	for(int i=1;i<=n;i++) vis[i]=0;
	for(int i=1;i<=n;i++) tmp[i].clear();
	for(int i=2;i<=n;i++) tmp[f[i]].push_back(i);
	bool ttt=check(1);
	if(!ttt) return INF;
	for(int i=1;i<=n;i++) if(!vis[i]) return INF;
	memcpy(x,bx,sizeof x);
	memcpy(y,by,sizeof y);
	set<node>s;
	for(int i=2;i<=n;i++) s.insert((node){x[i],y[i],i});
	for(int i=1;i<=n;i++) fa[i]=i;
	while(s.size()){
		int u=(*s.begin()).id;
		s.erase(*s.begin());
		int ffu=find(f[u]);
		fa[u]=ffu;
		if(ffu!=1) s.erase((node){x[ffu],y[ffu],ffu});
		merge(ffu,u);
		if(ffu!=1) s.insert((node){x[ffu],y[ffu],ffu});
	}
	return x[1];
}
void dfs(int x){
	if(x==n+1){
		ret=min(ret,calc());
		return;
	}
	for(int i=0;i<fedge[x].size();i++){
		f[x]=fedge[x][i];
		dfs(x+1);
	}
}
int solve2(){
	for(int i=1;i<=n;i++) y[i]-=x[i],x[i]=max(x[i],y[i]);
	memcpy(bx,x,sizeof bx);
	memcpy(by,y,sizeof by);
	dfs(2);
	return ret;
}
signed main(){
	int u,v;
	cin>>n>>m;
	for(int i=2;i<=n;i++) scanf("%lld%lld",&x[i],&y[i]);
	for(int i=1;i<=m;i++){
		scanf("%lld%lld",&u,&v);
		edge[u].push_back(v);
		fedge[v].push_back(u);
	}
	if(n<=26) cout<<solve1()<<endl;
	else cout<<solve2()<<endl;
	return 0;
}