// Saarland University: <(OvO)>
#include <bits/stdc++.h>

#define sz(a) ((int)(a).size())
#define divceil(a, b) ((a) + (b) - 1) / (b)

using namespace std;

#ifdef ONPC
    string to_string(const char* s) {
        return s;
    }
    template<typename T>
    string to_string(const T& cont) {
        string ans = "";
        for (bool fst = true; const auto& val: cont) {
            if (!fst) {
                ans += ", ";
            }
            ans += to_string(val);
            fst = false;
        }
        return ans + "}";
    }

    void debug_print_collection() {
        cerr << endl;
    }

    template<typename First, typename... Args>
    void debug_print_collection(First val, Args... args) {
        cerr << "   " << to_string(val);
        debug_print_collection(args...);
    }
    #define debug(...) { cerr << "@@@ [" << #__VA_ARGS__ << "] ="; debug_print_collection(__VA_ARGS__);}
    #else
    #define debug(...) ;
    #define NDEBUG
#endif

mt19937 rnd(123);

typedef long long ll;
typedef long double ld;

int solve() {
    int n;
    if (!(cin >> n)) {
        return 1;
    }
    vector<vector<vector<int>>> a(3, vector<vector<int>>(3));
    string A, B;
    cin >> A >> B;
    auto get_val = [&](char c) {
        if (c == '-') {
            return 0;
        } else if (c == 'M') {
            return 1;
        } else {
            return 2;
        }
    };
    vector<pair<int, int>> tp(n);
    for (int i = 0; i < n; i++) {
        if (A[i] == B[i]) {
            continue;
        }
        a[get_val(A[i])][get_val(B[i])].push_back(i);
        tp[i] = make_pair(get_val(A[i]), get_val(B[i]));
    }
    vector<vector<int> > ans;
    for(int k = 1; k <= 2; k ++) {
        while(a[0][k].size()) {
            int cur = a[0][k].back();
            a[0][k].pop_back();
            int c = k;
            if(a[c][3-c].empty() && a[c][0].empty()) {
                continue;
            }
            ans.push_back({cur, 0, 1});
            while(a[c][3 - c].size()) {
                int next = a[c][3-c].back();
                a[c][3-c].pop_back();
                int ispickup = 1;
                if(a[3-c][c].empty() && a[3-c][0].empty())
                    ispickup = 0;
                ans.push_back({next, 1, ispickup});
                c = 3 - c;
            }
            if(a[c][0].size()) {
                int next = a[c][0].back();
                a[c][0].pop_back();
                ans.push_back({next, 1, 0});
            }
        } 
    }
    cout << ans.size() << '\n';
    for(auto x : ans)
    {
        cout << "DRIVE " << x[0]+1 << '\n';
        if(x[1])
            cout << "DROPOFF\n";
        if(x[2])
            cout << "PICKUP\n";
    }

    return 0;
}

int32_t main() {
    #ifdef ONPC
    assert(freopen("G.txt", "r", stdin));
    #endif
    int TET = 1e9;
    // cin >> TET;
    for (int i = 1; i <= TET; i ++) { 
        if (solve()) {
            break;
        }
        #ifdef ONPC
            cout << "__________________" << endl;
        #endif 
    }
    #ifdef ONPC
        cerr << endl << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl;
    #endif
}


/*

g++ -std=c++20 -Wall -Wextra -Wshadow -D_GLIBCXX_DEBUG -DONPC -O2 -fsanitize=address -fsanitize=undefined -fno-sanitize-recover -o ex template.cpp && ./ex

*/