#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
const int M = 100005;
#define int long long
#define pb push_back
int read()
{
	int x=0,f=1;char c;
	while((c=getchar())<'0' || c>'9') {if(c=='-') f=-1;}
	while(c>='0' && c<='9') {x=(x<<3)+(x<<1)+(c^48);c=getchar();}
	return x*f;
}
int n,m,a[M],b[M],c[M],f[M],p[M],in[M],fa[M];
vector<int> g[M],G[M];
int find(int x)
{
	if(x==fa[x]) return x;
	return fa[x]=find(fa[x]);
}
void dfs(int u)
{
	f[u]=c[u];
	for(int v:G[u])
	{
		dfs(v);b[u]+=b[v];
		f[u]=min(f[u],max(f[v],c[u]-b[v]));
	}
}
signed main()
{
	n=read();m=read();
	for(int i=1;i<=n;i++)
	{
		a[i]=read();b[i]=read();
		c[i]=max(a[i]-b[i],0ll);
		p[i]=fa[i]=i;
	}
	for(int i=1;i<=m;i++)
	{
		int u=read(),v=read();
		g[u].pb(v);g[v].pb(u);
	}
	sort(p+1,p+1+n,[&](int i,int j)
		{return c[i]<c[j];});
	for(int i=1;i<=n;i++)
	{
		int u=p[i];in[u]=1;
		for(int v:g[u])
			if(in[v] && find(u)^find(v))
			{
				G[u].pb(find(v));
				fa[find(v)]=find(u);
			}
	}
	int rt=p[n];dfs(rt);
	printf("%lld\n",f[rt]+b[rt]);
}