#include <bits/stdc++.h>

using namespace std;

void even_out(vector<vector<vector<int>>>& edges) {
    int c_in = edges[0][2].size() + edges[1][2].size();
    int c_out = edges[2][0].size() + edges[2][1].size();

    assert(c_in >= c_out);

    for (; c_out < c_in; c_out++) {
        edges[2][0].push_back(-1);
    }

    int b_in = edges[1][0].size() + edges[1][2].size();
    int b_out = edges[0][1].size() + edges[2][1].size();

    assert(b_in >= b_out);

    for (; b_out < b_in; b_out++) {
        edges[1][0].push_back(-1);
    }
}

bool solved(auto& edges) {
    int sum = edges[1][0].size() + edges[1][2].size() + edges[2][0].size() + edges[2][1].size();
    return (sum == 0);
}

void euler(int node, vector<vector<vector<int>>>& edges, vector<int>& walk) {
    // cerr << node << endl;
    for (int i = 2; i >= 0; i--) {
        while(!edges[node][i].empty()) {
            int edge = edges[node][i].back();
            edges[node][i].pop_back();
            euler(i, edges, walk);
            walk.push_back(edge);
        }
    }
}

string itoa(int i) {
    string s;
    do {
        s += (i % 10 + '0');
        i /= 10;
    } while (i > 0);
    reverse(s.begin(), s.end());
    return s;
}

void Solve() {
    map<char, int> mp;
    mp['-'] = 0;
    mp['M'] = 1;
    mp['C'] = 2;

    int n; cin >> n;
    string bui; cin >> bui;
    string prof; cin >> prof;

    vector<vector<vector<int>>> edges(3, vector<vector<int>>(3));
    for (int i = 0; i < n; i++) {
        edges[mp[bui[i]]][mp[prof[i]]].push_back(i);
    }

    for (int i = 0; i < 3; i++) {
        edges[i][i].clear();
    }

    // for (int i = 0; i < 3; i++) {
    //     for (int j = 0; j < 3; j++) {
    //         cerr << edges[i][j].size() << " ";
    //     }
    //     cerr << endl;
    // }

    if (solved(edges)) {
        cout << "0\n";
        return;
    }

    even_out(edges);

    vector<int> walk;
    euler(0, edges, walk);
    reverse(walk.begin(), walk.end());

    // for (auto& i : walk) {
    //     cerr << i << " ";
    // }
    // cerr << endl;

    vector<string> ans;
    bool on = false;
    for (auto& i : walk) {
        if (i == -1) { continue; }
        ans.push_back("DRIVE " + itoa(i + 1));
        if (on) { ans.push_back("DROPOFF"); on = false; }
        if (prof[i] != '-') { ans.push_back("PICKUP"); on = true; }
    }

    cout << ans.size() << "\n";
    for (auto& line : ans) {
        cout << line << "\n";
    }
}

int main() {
    Solve();
}