#pragma GCC optimize("Ofast")
#pragma GCC target("avx2,bmi2,lzcnt,fma")

#include<bits/stdc++.h>
using namespace std;

vector<pair<int, int>> solve(vector<int> A, vector<int> B, vector<pair<int, int>> E)
{
    int N = A.size();
    vector<vector<int>> conn(N);
    vector<vector<bool>> adj(N, vector<bool>(N));
    for(auto& [u, v]: E)
    {
        if(u > v) swap(u, v);
        conn[u].push_back(v), conn[v].push_back(u);
        adj[v][u] = adj[u][v] = 1;
    }
    sort(E.begin(), E.end());

    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> Q;
    vector<int> deg(N), color(N, -1);
    for(int i=0; i<N; ++i) deg[i] = conn[i].size(), Q.emplace(deg[i], i);


    while(!Q.empty())
    {
        int u = Q.top().second; Q.pop();
        if(color[u] != -1) continue;
        vector<bool> exist(conn[u].size()+1);
        for(int v: conn[u])
        {
            Q.emplace(deg[v]--, v);
            if(color[v] != -1 && color[v] < (int)exist.size()) exist[color[v]] = 1;
        }
        for(int i=0; i<(int)exist.size(); ++i) if(!exist[i])
        {
            color[u] = i;
            break;
        }
        assert(color[u] != -1);
    }

    int K = 1+*max_element(color.begin(), color.end());
    vector<vector<int>> cliques(K);
    for(int i=0; i<N; ++i) cliques[color[i]].push_back(i);

    auto cmp = [&](int x, int y)
    {
        if(x == y) return false;
        if(x < y) return A[x] < B[y];
        return B[x] < A[y];
    };

    function<void(vector<int>::iterator, vector<int>::iterator)> hamiltonian = [&](vector<int>::iterator st, vector<int>::iterator ed)
    {
        int N = distance(st, ed);
        if(N == 1) return;

        auto mi = st + N / 2;
        hamiltonian(st, mi); hamiltonian(mi, ed);

        vector<int> buffer; buffer.reserve(N);
        auto l = st, r = mi;
        while(l != mi || r != ed)
        {
            if(l == mi) buffer.push_back(*r++);
            else if(r == ed) buffer.push_back(*l++);
            else if(cmp(*l, *r)) buffer.push_back(*l++);
            else buffer.push_back(*r++);
        }
        copy(buffer.begin(), buffer.end(), st);
        return;
    };

    auto exist = [&](int u, int v)
    {
        return cmp(u, v) && !adj[u][v];
    };


    vector<pair<int, int>> ans;
    for(int i=0; i<K; ++i)
    {
        hamiltonian(cliques[i].begin(), cliques[i].end());
        for(int j=0; j<(int)cliques[i].size()-1; ++j)
            ans.emplace_back(cliques[i][j], cliques[i][j+1]);
    }


    for(int i=0; i<K; ++i)
        for(int j=i; j<K; ++j)
        {
            for(int u: cliques[j])
            {
                for(int k=0; k<(int)cliques[i].size(); ++k)
                {
                    int v = cliques[i][k];
                    if(exist(u, v))
                    {
                        ans.emplace_back(u, v);
                        break;
                    }
                }
                if(i != j)
                    for(int k=(int)cliques[i].size()-1; k>=0; --k)
                    {
                        int v = cliques[i][k];
                        if(exist(v, u))
                        {
                            ans.emplace_back(v, u);
                            break;
                        }
                    }
            }
        }

    sort(ans.begin(), ans.end());
    ans.erase(unique(ans.begin(), ans.end()), ans.end());

    return ans;
}

int main()
{
    ios::sync_with_stdio(false); cin.tie(0);
    int N, M; cin >> N >> M;
    vector<int> A(N), B(N);
    for(int&x: A) cin >> x;
    for(int&x: B) cin >> x;
    vector<pair<int, int>> E(M);
    for(auto& [u, v]: E)
    {
        cin >> u >> v;
        --u; --v;
    }
    auto ret = solve(A, B, E);
    cout << ret.size() << '\n';
    for(auto [a, b]: ret)
        cout << a+1 << " " << b+1 << '\n';
}