#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define f first
#define s second
const int N = 2e5 + 4;
string s, t;
vector < int > mc, cm, m, c, emp, startc, startm;
set < int > need;

void find() {
    int n;
    cin >> n >> s >> t;
    mc.clear ();
    cm.clear ();
    c.clear ();
    m.clear ();
    startc.clear ();
    startm.clear ();
    for (int i = 0; i < n; ++i) {
        if (t[i] != '-' && s[i] != t[i]) need.insert(i + 1);

        if (t[i] == '-') {
            if (s[i] == '-') emp.push_back(i + 1);
            else if (s[i] == 'C') c.push_back(i + 1);
            else m.push_back(i + 1);
        }
        else {
            if (t[i] == 'C') {
                if (s[i] == '-') startc.push_back(i + 1);
                else if (s[i] == 'M') mc.push_back(i + 1);
            }
            else {
                if (s[i] == '-') startm.push_back(i + 1);
                else if (s[i] == 'C') cm.push_back(i + 1);
            }
        }
    }
    vector < pair < string , int > > res;
    while (1) {
        int start, turn; // 1 - cm, 2 - mc;
        if (!startc.empty ()) {
            start = startc.back ();
            startc.pop_back ();
            turn = 1;
        }
        else if (!startm.empty ()) {
            start = startm.back ();
            startm.pop_back ();
            turn = 2;
        }
        else {
            break;
        }
        int ok = 0;
        res.push_back({"DRIVE ", start});
        while (1) {
            res.push_back({"PICKUP ", -1});
            if (turn == 1) {
                if (!cm.empty ()) {
                    int to = cm.back ();
                    cm.pop_back ();
                    res.push_back({"DRIVE ", to});
                    res.push_back({"DROPOFF", -1});
                    ok = 1;
                    start = to;
                    turn = 2;
                }
                else {
                    if (!c.empty ()) {
                        int to = c.back ();
                        c.pop_back ();
                        res.push_back({"DRIVE ", to});
                        res.push_back({"DROPOFF", -1});
                        ok = 1;
                        break ;
                    }
                    else {
                        res.pop_back ();
                        break;
                    }
                }
            }
            else {
                if (!mc.empty ()) {
                    int to = mc.back ();
                    mc.pop_back ();
                    res.push_back({"DRIVE ", to});
                    res.push_back({"DROPOFF", -1});
                    ok = 1;
                    start = to;
                    turn = 1;
                }
                else {
                    if (!m.empty ()) {
                        int to = m.back ();
                        m.pop_back ();
                        res.push_back({"DRIVE ", to});
                        res.push_back({"DROPOFF", -1});
                        ok = 1;
                        break ;
                    }
                    else {
                        res.pop_back ();
                        break;
                    }
                }
            }
        }
    }
    cout << res.size () <<  "\n";
    for (auto i : res) {
        cout << i.first;
        if (i.second != -1) cout << i.second;
        cout << "\n";
    }
}

int32_t main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    while (t--) {
        find();
    }
    return 0;
}