#include <bits/stdc++.h>

using namespace std;

bool DIR = true;

struct EulerWalk {
    int n;
    vector<vector<pair<int, int>>> graph;
    vector<int> cap, walk, buf, deg;

    EulerWalk(int n): n(n), graph(n + 1), deg(n + 1) {}

    int AddEdge(int a, int b, int c = 1) {
        int ret = cap.size();
        graph[b].emplace_back(a, ret);
        if(!DIR) graph[a].emplace_back(b, ret);
        cap.push_back(c);
        deg[a] += c;
        deg[b] -= c;
        if(!DIR) deg[a] %= 2, deg[b] %= 2;

        return ret;
    }

    void dfs(int node) {
        while(graph[node].size()) {
            auto [vec, ei] = graph[node].back();
            if(!cap[ei]) graph[node].pop_back();
            else --cap[ei], dfs(vec);
        }
        walk.push_back(node);
    }

    template<typename CB>
    void Go(CB&& cb) {
        for(int i = 0; i <= n; ++i) {
            if(deg[i] < 0) AddEdge(i, n, -deg[i]);
            if(deg[i] > 0) AddEdge(n, i, +deg[i]);
            assert(deg[i] == 0);
        }

        for(int i = n; i >= 0; --i) {
            dfs(i), walk.push_back(n);
        }

        for(int i = 0, j = 0; i < (int)walk.size(); i = j + 1) {
            for(j = i; walk[j] < n; ++j);
            if(j - i > 1) cb(walk.begin() + i, walk.begin() + j);
        }
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int n;
    cin >> n;

    string arrive, depart;
    cin >> depart;
    cin >> arrive;

    vector<vector<pair<int, int>>> graph(3);
    unordered_map<char, int> char_to_pos;

    char_to_pos['M'] = 0;
    char_to_pos['C'] = 1;
    char_to_pos['-'] = 2;

    EulerWalk ew(3);

    vector<vector<int>> ids(9);
    for(int i = 0; i < n; i++) {
        if(arrive[i] == depart[i])continue;
        ew.AddEdge(char_to_pos[arrive[i]], char_to_pos[depart[i]]);
        ids[char_to_pos[arrive[i]] * 3 + char_to_pos[depart[i]]].push_back(i);
    }

  
    int count = 0;
    ostringstream answer;

    ew.Go([&] (vector<int>::iterator begin, vector<int>::iterator end) {
        vector<int> walk;
        for(auto it = begin, nit = next(it); nit != end; it++, nit++) {
            walk.push_back(ids[*it * 3 + *nit].back());
            ids[*it * 3 + *nit].pop_back();
        }
        reverse(walk.begin(), walk.end());
        for(int i = 0; i < (int)walk.size(); i++) {
            count += 1;
            answer << "DRIVE " << walk[i] + 1 << "\n";
            if(depart[walk[i]] != '-') {
                count += 1;
                answer << "DROPOFF\n";
            }
            if(arrive[walk[i]] != '-') {
                count += 1;
                answer << "PICKUP\n";
            }
        }
    });

    cout << count << "\n";
    cout << answer.str();


    return 0;
}