#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using db = double;
using vi = vector<int>;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
#define debug(x) cout << #x <<'	' << x <<endl
const int inf = 0x3f3f3f3f;
const db eps = 1e-8;
const int mod = 1e9+7;
ll qpow(ll a, ll b){
    ll ret = 1;
    while(b){
        if(b&1)ret = ret*a%mod;
        a = a*a%mod;
        b>>=1;
    }
    return ret;
}

const int maxn = 200010;
int n, m;
ll a[maxn], b[maxn], sum[maxn], f[maxn], p[maxn], dp[maxn], vis[maxn];
int Find(int x){
	return f[x] == x?x:f[x]=Find(f[x]);
} 
vector<int>G[maxn];
bool cmp(int x, int y){
	return a[x] < a[y];
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n >> m;
	for(int i=1; i<=n; ++i){
		cin >> a[i] >> b[i];
		a[i] = max(a[i]-b[i], 0ll);
		p[i] = f[i] = i;
		sum[i] = b[i];
		dp[i] = a[i];
	}
	for(int i=0, u, v; i<m; ++i){
		cin >> u >> v;
		G[v].pb(u);
		G[u].pb(v);
	}
	sort(p+1, p+1+n, cmp);
	for(int i=1; i<=n; ++i){
		int u = p[i];
		vis[u] = 1;
		for(auto v:G[u]){
			if(vis[v]){
				int x = Find(u), y = Find(v);
				if(x!=y){
					f[y] = x;
					sum[x] += sum[y];
					dp[x] = min(dp[x], max(dp[y], a[x]-sum[y]));
				}
			}
		}
	} 
	cout << dp[Find(1)] + sum[Find(1)] <<"\n";
}
