#include<bits/stdc++.h>
#define int long long
using namespace std;
int a[105],b[105],n,m;
void cmin(int &x,int y){x=(x<y?x:y);}
const int inf=0x3f3f3f3f3f3f3f3f;
namespace Sub1
{
	int dp[1<<26],e[20],u,v;
	void main()
	{
		for(int i=1;i<=m;i++)
		{
			cin>>u>>v;u--;v--;
			e[u]|=(1<<v);e[v]|=(1<<u);
		}
		for(int s=0;s<(1<<n);s++)dp[s]=inf;
		dp[1]=a[1];
		for(int s=1;s<(1<<n);s++)
		{
			int t=0;
			for(int i=0;i<n;i++)if(s&(1<<i))t|=e[i];
			int now=dp[s];
			for(int i=0;i<n;i++)if(s&(1<<i))now-=a[i+1],now+=b[i+1];
			for(int i=0;i<n;i++)
			{
				if(s&(1<<i))continue;
				if(!(t&(1<<i)))continue;
				cmin(dp[s|(1<<i)],dp[s]+max(0ll,a[i+1]-now));
			}
		}
		cout<<dp[(1<<n)-1];
	}
}
signed main()
{
	cin.tie(0)->sync_with_stdio(0);
	cin>>n>>m;
	for(int i=2;i<=n;i++)cin>>a[i]>>b[i];
	if(n<=25)Sub1::main();
	return 0;
}