#include "bits/stdc++.h"
using namespace std;
using LL = long long;
using ll = long long;

#define all(x) begin(x),end(x)

const int E = 2, C = 0, M = 1;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int n; cin >> n;
	vector<int> v[3][3]; // need, have
	string s, t; cin >> s >> t;
	for(int i = 0; i < n; ++i){
		int x = E; if(s[i] == 'C') x = C; if(s[i] == 'M') x = M;
		int y = E; if(t[i] == 'C') y = C; if(t[i] == 'M') y = M;
		v[x][y].push_back(i+1);
	}
	// 0M source of math, 0C source of cs
	// if any 0M start from him, do as many MC-CM as possible, then end at (M/C)0 or any MM CC 00
	// if any 0C start from him, do as many CM-MC as possible, then end at (M/C)0 or any MM CC 00
	// if any 0M or 0C left, dump them into M0 and C0 and even CM/MC (can there still be any?)
	auto cnt = [&](int t, int tt){
		return v[t][tt].size();
	};
	auto need = [&](int t){
		return v[t][E].size() + v[t][1^t].size();
	};
	int anslen = 0;
	string ans;
	auto go = [&](int t, int tt){
		int i = v[t][tt].back(); v[t][tt].pop_back();
		ans += "DRIVE "; ans += to_string(i); ans += "\n";
		++anslen;

	};
	auto pick = [&](){
		ans += "PICKUP\n";
		++anslen;
	};
	auto drop = [&](){
		ans += "DROPOFF\n";
		++anslen;
	};
	while(need(M) + need(C)){
		assert(cnt(E, M) + cnt(E, C));
		int curr = E;
		if(need(M) && cnt(E, M)){ // start with a M
			go(E, M);
			pick();
			curr = M;
		}
		else if(need(C) && cnt(E, C)){ // start with a C
			go(E, C);
			pick();
			curr = C;
		}
		assert(curr != E);
		while(curr != E && need(curr)){
			if(cnt(curr, 1^curr)){ // swap
				go(curr, 1^curr);
				drop();
				// devo pickare?
				if(need(1^curr)){
					curr ^= 1;
					pick();
				}
				else curr = E;
			}
			else { // dst
				go(curr, E);
				drop();
				curr = E;
			}		
		}
		if(curr != E){
			drop();
			curr = E;
		}
	}
	cout << anslen << endl;
	cout << ans << endl;
}