#include <bits/stdc++.h>
using namespace std;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define REP(i, n) FOR(i,0,n)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define IREP(i, n) IFOR(i,0,n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(),v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x) distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define Max(a, b) a = max(a, b)
#define Min(a, b) a = min(a, b)
#define bit(n) (1LL<<(n))
#define Ans(f, y, n) if(f) cout << y << endl; else cout << n << endl;
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v) cout << #v << "=" << endl; REP(i, v.size()){ cout << v[i] << ","; } cout << endl;
#define mdebug(m) cout << #m << "=" << endl; REP(i, m.size()){ REP(j, m[i].size()){ cout << m[i][j] << ","; } cout << endl;}
#define pb push_back
#define int long long
#define INF 1000000000000000000

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PiP = pair<int, Pii>;
using PPi = pair<Pii, int>;
using bools = vector<bool>;
using pairs = vector<Pii>;

template<typename T> void readv(vector<T> &a){ REP(i, a.size()) cin >> a[i]; }
void readv_m1(vector<int> &a){ REP(i, a.size()){cin >> a[i]; a[i]--;} }

//int dx[4] = {1,0,-1,0};
//int dy[4] = {0,1,0,-1};

int mod = 1000000007;
//int mod = 998244353;
#define Add(x, y) x = (x + (y)) % mod
#define Mult(x, y) x = (x * (y)) % mod
#define AddMult(x, y, z) x = (x + (y) * (z)) % mod

struct edge{int to, cost;};

class Graph
{
public:
    int N;
    vector<vector<edge>> G;

    Graph(int N): N(N){
        G = vector<vector<edge>>(N, vector<edge>(0));
    }

    void add_edge(int from, int to, int cost = 0){
        G[from].push_back(edge({to, cost}));
    }

    void add_edge2(int v1, int v2, int cost = 0){
        add_edge(v1, v2, cost);
        add_edge(v2, v1, cost);
    }

};

class Union_find
{
public:
    vector<int> par;
    vector<int> sz, ans, get;

    Union_find(int N, vec A, vec B){
        par = vector<int>(N);
        REP(i, N) par[i] = i;
        sz = vector<int>(N, 1);
        ans = A;
        get = B;
    }

    int find(int x){
        if(par[x] == x) return x;
        else return par[x] = find(par[x]);
    }

    void unite(int x, int y){
        x = find(x);
        y = find(y);
        if(x == y) return;

        //int tmp = ans[x];
        //if(sz[x] < sz[y]) swap(x, y);

        par[y] = x;
        sz[x] += sz[y];
        get[x] += get[y];
        //ans[x] = tmp;
    }

    bool is_union(int x, int y){
        x = find(x);
        y = find(y);
        return x == y;
    }

    int union_size(int x){
        return sz[find(x)];
    }

    void unite2(int x, int y, vec &A){
        if(is_union(x, y)) return;
        y = find(y);
        Min(ans[x], max(ans[y], A[x] - get[y]));
        unite(x, y);

    }

};

signed main(){

    int N, M; cin >> N >> M;
    Graph G(N);
    vec A(N), B(N);
    pairs p(N);
    REP(i, N){
        cin >> A[i] >> B[i];
        A[i] = max(0LL, A[i] - B[i]);
        p[i] = Pii(A[i], i);
    }
    Sort(p);
    int U, V;
    REP(i, M){
        cin >> U >> V;
        G.add_edge2(U - 1, V - 1);
    }

    Union_find UF(N, A, B);
    bools used(N, false);
    REP(i, N){
        int i0 = p[i].second;
        for(auto e: G.G[i0]) if(used[e.to]) UF.unite2(i0, e.to, A);
        used[i0] = true;
    }
    int ans = UF.ans[p[N - 1].second];
    REP(i, N) ans += B[i];
    cout << ans << endl;


    return 0;
}


Measured memory_bytes: 15616