#include <bits/stdc++.h>

using namespace std;

void print_ans(vector<int> res, vector<int> have, vector<int> need) {
    int n = res.size();
    for (int i = 0; i < n; ++i) {
        cout << "DRIVE " << res[i] + 1 << "\n";
        if (need[res[i]]) {
            cout << "DROPOFF\n";
        }
        if (have[res[i]]) {
            cout << "PICKUP\n";
        }
    }
}

int main() {
    cin.tie(nullptr);
    cout.tie(nullptr);
    iostream::sync_with_stdio(false);
    int cnt[3][3]; // 0 n 1 m 2 c
    for (int i = 0; i < 3; ++i)
        for (int j = 0; j < 3; ++j)
            cnt[i][j] = 0;
    vector<int> inds[3][3];
    int n;
    cin >> n;
    string t;
    cin >> t;
    string s;
    cin >> s;
    vector<int> have(n);
    vector<int> need(n);
    for (int i = 0; i < n; ++i) {
        int id1;
        if (s[i] == '-')
            id1 = 0;
        if (s[i] == 'M')
            id1 = 1;
        if (s[i] == 'C')
            id1 = 2;
        have[i] = id1;
        int id2;
        if (t[i] == '-')
            id2 = 0;
        if (t[i] == 'M')
            id2 = 1;
        if (t[i] == 'C')
            id2 = 2;
        need[i] = id2;
        cnt[id1][id2]++;
        inds[id1][id2].push_back(i);
    }
    vector<int> res; // -1 dropoff -2 pickup
    pair<int, int> start = {0, 0};
    while (cnt[2][1] + cnt[1][2] + cnt[0][1] + cnt[0][2] > 0) {
        bool dropoff = false;
        if (start == make_pair(2, 0)) {
            start = {2, 2};
            res.push_back(-2);
            cnt[2][0]--;
        }
        else if (start == make_pair(1, 0)) {
            start = {1, 1};
            res.push_back(-2);
            cnt[1][0]--;
        }
        else if (start == make_pair(2, 1)) {
            start = {2, 2};
            res.push_back(-1);
            res.push_back(-2);
            cnt[2][1]--;
        }
        else if (start == make_pair(1, 2)) {
            start =  {1, 1};
            res.push_back(-1);
            res.push_back(-2);
            cnt[1][2]--;
        }
        else if (start == make_pair(0, 1)) {
            start = {0, 0};
            res.push_back(-1);
            cnt[0][1]--;
        }
        else if (start == make_pair(0, 2)) {
            start = {0, 0};
            res.push_back(-1);
            cnt[0][2]--;
        }
        else if (start == make_pair(1, 1)) {
            if (cnt[2][1])
                start = {2, 1};
            else if (cnt[0][1])
                start = {0, 1};
            else if (cnt[2][0])
                start = {2, 0}, dropoff=true;
            else {
                assert(false);
            }
        }
        else if (start == make_pair(2, 2)) {
            if (cnt[1][2])
                start = {1, 2};
            else if (cnt[0][2])
                start = {0, 2};
            else if (cnt[1][0])
                start = {1, 0}, dropoff=true;
            else {
                assert(false);
            }
        }
        else if (start == make_pair(0, 0)) {
            if (cnt[1][0]) {
                start = {1, 0};
            }
            else if (cnt[2][0]) {
                start = { 2, 0 };
            }
            else {
                assert(false);
            }
        }
        if (start.first != start.second) {
            res.push_back(inds[start.first][start.second].back());
            inds[start.first][start.second].pop_back();
        }
        if (dropoff) {
            res.push_back(-1);
        }
    }
    cout << res.size() << "\n";
    for (int x: res) {
        if (x == -2) {
            cout << "PICKUP\n";
        }
        else if (x == -1) {
            cout << "DROPOFF\n";
        }
        else {
            cout << "DRIVE " << x + 1 << "\n";
        }
    }
}