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


int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n;
    cin >> n;
	string course, prof;
	cin >> course >> prof;

	vector <pair <string, int>> operations;
	vector <int> solved(n);

	for (int i = 0; i < n; i++)
		solved[i] = (course[i] == prof[i]);

	string t = "CM";
	int have_type = -1;
	
	while (true) {
		// try to dropoff somewhere, preferably with another prof
		if (have_type != -1) {
			int course_no_prof = -1, course_prof = -1;
			for (int i = 0; i < n; i++) {
				if (!solved[i] && course[i] == t[have_type]) {
					if (prof[i] != '-')
						course_prof = i;
					else
						course_no_prof = i;
				}
			}
			if (course_prof != -1) {
				operations.push_back({ "DRIVE", course_prof });
				operations.push_back({ "DROPOFF", -1 });
				operations.push_back({ "PICKUP", -1 });
				solved[course_prof] = 1;
				have_type = 1 - have_type;
				continue;
			}
			if (course_no_prof != -1) {
				operations.push_back({ "DRIVE", course_no_prof });
				operations.push_back({ "DROPOFF", -1 });
				solved[course_no_prof] = 1;
				have_type = -1;
				continue;
			}
		}

		// don't have anyone, of who we have is useless.
		// we have to pickup some random prof and try to do something with him
		bool done_something = false;
		for (int i = 0; i < n; i++) {
			if (!solved[i] && course[i] == '-' && prof[i] != '-') {
				operations.push_back({ "DRIVE", i });
				if (have_type != -1) {
					operations.push_back({ "DROPOFF", -1 });
					have_type = -1;
				}
				operations.push_back({ "PICKUP", -1 });
				have_type = (prof[i] == 'M');
				solved[i] = 1;
				done_something = true;
				break;
			}
		}

		if (!done_something)
			break;
	}

	cout << operations.size() << '\n';

	for (auto [s, nr] : operations) {
		cout << s;
		if (nr != -1)
			cout << " " << nr + 1;
		cout << '\n';
	}
}