#include <bits/stdc++.h>
using namespace std;

enum Op {
    DRIVE,
    PICKUP,
    DROPOFF
};

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

    string s1;
    string s2;

    int n;
    cin >> n;
    cin >> s1 >> s2;
    vector<int> M, C, MC, CM, C_, M_;
    for (int i = 0; i < n; ++i) {
        if (s1[i] == '-' && s2[i] == 'C')
            C.push_back(i);
        if (s1[i] == '-' && s2[i] == 'M')
            M.push_back(i);
        if (s1[i] == 'M' && s2[i] == 'C')
            MC.push_back(i);
        if (s1[i] == 'C' && s2[i] == 'M')
            CM.push_back(i);
        if (s1[i] == 'C' && s2[i] == '-')
            C_.push_back(i);
        if (s1[i] == 'M' && s2[i] == '-')
            M_.push_back(i);
    }

    int last = -1;
    char tip;
    vector<pair<Op, int>> v;
    while (!M.empty() || !C.empty() || last != -1) {
        if (last == -1) {
            if (!M.empty()) {
                last = M.back();
                M.pop_back();
                tip = 'M';
                v.push_back({Op::DRIVE, last});
                v.push_back({Op::PICKUP, 0});
            } else if (!C.empty()) {
                last = C.back();
                C.pop_back();
                tip = 'C';
                v.push_back({Op::DRIVE, last});
                v.push_back({Op::PICKUP, 0});
            }
        } else {
            if (tip == 'M') {
                if (!MC.empty()) {
                    last = MC.back();
                    MC.pop_back();
                    tip = 'C';
                    v.push_back({Op::DRIVE, last});
                    v.push_back({Op::DROPOFF, 0});
                    v.push_back({Op::PICKUP, 0});
                } else if (!M_.empty()) {
                    last = -1;
                    v.push_back({Op::DRIVE, M_.back()});
                    M_.pop_back();
                    v.push_back({Op::DROPOFF, 0});
                } else {
                    last = -1;
                    v.pop_back();
                }

            } else if (tip == 'C') {
                if (!CM.empty()) {
                    last = CM.back();
                    CM.pop_back();
                    tip = 'M';
                    v.push_back({Op::DRIVE, last});
                    v.push_back({Op::DROPOFF, 0});
                    v.push_back({Op::PICKUP, 0});
                } else if (!C_.empty()) {
                    last = -1;
                    v.push_back({Op::DRIVE, C_.back()});
                    C_.pop_back();
                    v.push_back({Op::DROPOFF, 0});
                } else {
                    last = -1;
                    v.pop_back();
                }
            }
        }
    }


//    if (!v.empty() && v.back().first == Op::PICKUP)
//        v.pop_back();

    cout << v.size() << "\n";

    for (auto it : v) {
        if (it.first == Op::DRIVE)
            cout << "DRIVE " << it.second + 1 << "\n";
        else if (it.first == Op::PICKUP)
            cout << "PICKUP\n";
        else
            cout << "DROPOFF\n";
    }

    assert (C_.empty() && M_.empty() && MC.empty() && CM.empty());

    return 0;
}