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

#include <bits/stdc++.h>
#include <atcoder/segtree>

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}; }
using Seg = atcoder::segtree<pair<int, int>, op, 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;
    };

    vector<int> idxv(N);

    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 j=0; j<(int)cliques[i].size(); ++j)
            idxv[cliques[i][j]] = j;
    }


    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);
    Seg seg(2*N);

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

            vector<pair<bool, int>> V;
            for(int k=0; k<(int)cliques[i].size(); ++k) V.emplace_back(false, k);
            for(int k=0; k<(int)cliques[j].size(); ++k) V.emplace_back(true, k);

            sort(V.begin(), V.end(), [&](pair<int, int> a, pair<int, int> b)
            {
                int A = cliques[a.first?j:i][a.second];
                int B = cliques[b.first?j:i][b.second];
                if(A != B) return A < B;
                return a.first < b.first;
            });
            for(auto [tp, idx]: V)
            {
                if(tp)
                {
                    int u = cliques[j][idx];
                    for(int k=ptr[u]; k<(int)conn[u].size() && color[conn[u][k]] == i; ++k)
                        if(conn[u][k] < u) seg.set(A[conn[u][k]], e());

                    int maxv = seg.prod(0, B[u]).first;
                    int minv = seg.prod(B[u], 2*N).second;
                    io[idx] = op(io[idx], {maxv, minv});

                    for(int k=ptr[u]; k<(int)conn[u].size() && color[conn[u][k]] == i; ++k)
                        if(conn[u][k] < u) seg.set(A[conn[u][k]], {idxv[conn[u][k]], idxv[conn[u][k]]});
                }
                else seg.set(A[cliques[i][idx]], {idx, idx});
            }
            for(int x: cliques[i]) seg.set(A[x], e());
            assert(seg.all_prod() == e());

            sort(V.begin(), V.end(), [&](pair<int, int> a, pair<int, int> b)
            {
                int A = cliques[a.first?j:i][a.second];
                int B = cliques[b.first?j:i][b.second];
                if(A != B) return A > B;
                return a.first < b.first;
            });

            for(auto [tp, idx]: V)
            {
                if(tp)
                {
                    int u = cliques[j][idx];
                    for(int k=ptr[u]; k<(int)conn[u].size() && color[conn[u][k]] == i; ++k)
                        if(conn[u][k] > u) seg.set(B[conn[u][k]], e());

                    int maxv = seg.prod(0, A[u]).first;
                    int minv = seg.prod(A[u], 2*N).second;
                    io[idx] = op(io[idx], {maxv, minv});

                    for(int k=ptr[u]; k<(int)conn[u].size() && color[conn[u][k]] == i; ++k)
                        if(conn[u][k] > u) seg.set(B[conn[u][k]], {idxv[conn[u][k]], idxv[conn[u][k]]});
                }
                else seg.set(B[cliques[i][idx]], {idx, idx});
            }
            for(int x: cliques[i]) seg.set(B[x], e());
            assert(seg.all_prod() == e());

            for(int k=0; k<(int)cliques[j].size(); ++k)
            {
                auto [from, to] = io[k];
                int v = cliques[j][k];
                if(0 <= from && from < N && cliques[i][from] != v) ans.emplace_back(cliques[i][from], v);
                if(0 <= to && to < N && cliques[i][to] != v) ans.emplace_back(v, cliques[i][to]);
            }
        }
        for(int j=0; j<N; ++j) while(ptr[j] < (int)conn[j].size() && color[ptr[j]] == i) ++ptr[j];
    }

    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';
}