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

#include <bits/stdc++.h>

using namespace std;

pair<int, int> op(pair<int, int> a, pair<int, int> b) { return {max(a.first, b.first), min(a.second, b.second)}; }
pair<int, int> e() { return {INT_MIN, INT_MAX}; }

struct Node
{
    pair<int, int> val;
    Node *l, *r;
    Node(): val(e()), l(nullptr), r(nullptr) {}
    Node(int v): val({v, v}), l(nullptr), r(nullptr) {}
    Node(pair<int, int> v): val(v), l(nullptr), r(nullptr) {}
    Node(Node* l, Node *r): l(l), r(r) {
        val = op(l?l->val:e(), r?r->val:e());
    }

    Node* setv(int s, int e, int f, pair<int, int> v) const
    {
        if(s == e) return new Node(v);
        int m = (s+e)/2;
        if(f <= m) return new Node((l?l:new Node())->setv(s, m, f, v), r);
        else return new Node(l, (r?r:new Node())->setv(m+1, e, f, v));
    }


    Node* setv(int s, int e, int f, int v) const
    {
        return setv(s, e, f, {v, v});
    }

    pair<int, int> getv(int x, int y, int sv, int ev) const
    {
        if(x <= sv && ev <= y) return val;
        if(ev < x || y < sv) return e();
        int mv = (sv+ev)/2;
        return op(l?l->getv(x, y, sv, mv):e(), r?r->getv(x, y, mv+1, ev):e());
    }
};


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);
    for(auto& [u, v]: E)
    {
        if(u > v) swap(u, v);
        conn[u].push_back(v), conn[v].push_back(u);
    }
    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;
    };
    Node* blank = new Node();

    vector<int> idxv(N);

    vector<pair<int, int>> ans;
    auto cliques_by_number = cliques;
    vector<vector<Node*>> Aseg(K), Bseg(K);
    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 j=0; j<(int)cliques[i].size(); ++j)
            idxv[cliques[i][j]] = j;

        Aseg[i].resize(cliques[i].size());
        Bseg[i].resize(cliques[i].size());

        Node* as = blank;
        for(int j=0; j<(int)cliques[i].size(); ++j)
        {
            as = as->setv(0, 2*N-1, A[cliques_by_number[i][j]], idxv[cliques_by_number[i][j]]);
            Aseg[i][j] = as;
        }

        Node* bs = blank;
        for(int j=(int)cliques[i].size()-1; j>=0; --j)
        {
            bs = bs->setv(0, 2*N-1, B[cliques_by_number[i][j]], idxv[cliques_by_number[i][j]]);
            Bseg[i][j] = bs;
        }
    }


    for(int i=0; i<N; ++i) sort(conn[i].begin(), conn[i].end(), [&](int a, int b){
        return color[a] < color[b];
    });
    vector<int> ptr(N);

    for(int i=0; i<K; ++i)
    {
        for(int j=i; j<K; ++j)
        {
            vector<pair<int, int>> io(cliques[j].size(), e());

            for(int u: cliques[j])
            {
                int pos = distance(cliques_by_number[i].begin(),
                    lower_bound(cliques_by_number[i].begin(), cliques_by_number[i].end(), u));

                Node* Acur = (pos > 0) ? Aseg[i][pos-1] : blank;
                Node* Bcur = (pos < (int)cliques_by_number[i].size()) ? Bseg[i][pos] : blank;


                while(ptr[u]<(int)conn[u].size() && color[conn[u][ptr[u]]] == i)
                {
                    if(conn[u][ptr[u]] < u) Acur = Acur->setv(0, 2*N-1, A[conn[u][ptr[u]]], e());
                    else Bcur = Bcur->setv(0, 2*N-1, B[conn[u][ptr[u]]], e());
                    ++ptr[u];
                }


                int from = max(Acur->getv(0, B[u], 0, 2*N-1).first, Bcur->getv(0, A[u], 0, 2*N-1).first);
                int to = min(Bcur->getv(A[u], 2*N-1, 0, 2*N-1).second, Acur->getv(B[u], 2*N-1, 0, 2*N-1).second);

                if(0 <= from && from < N && cliques[i][from] != u) ans.emplace_back(cliques[i][from], u);
                if(0 <= to && to < N && cliques[i][to] != u) ans.emplace_back(u, cliques[i][to]);
            }

        }
    }

    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, --x;
    for(int&x: B) cin >> x, --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';
}