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

string to_string(string s) { return s; }
template <typename T> string to_string(T v) {
    string res = "[";
    for (const auto &x : v) {
        res += to_string(x) + ", ";
    }
    res += "]";
    return res;
}

void dbg_out() { cout << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) {
    cout << ' ' << to_string(H);
    dbg_out(T...);
}

#ifdef DEBUG
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

using ll = long long;
using vi = vector<int>;
#define rep(i, a, b) for (int i = (a); i < (b); ++i)
#define all(v) (v).begin(), (v).end()
#define sz(v) ((int)(v).size())

const int VIDE = 0;
const int M = 1;
const int C = 2;
vector <int> nb[3][3];

int to_const(char c)
{
    if (c == '-') return VIDE;
    if (c == 'M') return M;
    if (c == 'C') return C;
    return VIDE;
}

bool fini()
{
    return (nb[VIDE][C].size() == 0 ) && (nb[VIDE][M].size() == 0) && (nb[M][C].size() == 0) && (nb[C][M].size() == 0);
}

bool need_C()
{
    return (nb[VIDE][C].size() > 0) || (nb[M][C].size() > 0);
}

bool need_M()
{
    return (nb[VIDE][M].size() > 0) || (nb[C][M].size() > 0);
}

const int DRIVE = 5;
const int PICKUP = 6;
const int DROPOFF = 7;

vector <pair<int,int> > sol;

void peutM();
void peutC();
void rien();

void peutC()
{
    if (nb[M][C].size() > 0)
    {
        sol.push_back({PICKUP, 0});
        sol.push_back({DRIVE, nb[M][C].back()});
        nb[M][C].pop_back();
        sol.push_back({DROPOFF,0});
        peutM();
    }
    else if (nb[VIDE][C].size () > 0)
    {
        sol.push_back({PICKUP , 0});
        sol.push_back({DRIVE , nb[VIDE][C].back()});
        nb[VIDE][C].pop_back();
        sol.push_back({DROPOFF,0});
        rien();
    }
    else if (!fini()) assert(false);
}

void peutM()
{
    if (nb[C][M].size() > 0)
    {
        sol.push_back({PICKUP, 0});
        sol.push_back({DRIVE, nb[C][M].back()});
        nb[C][M].pop_back();
        sol.push_back({DROPOFF,0});
        peutC();
    }
    else if (nb[VIDE][M].size () > 0)
    {
        sol.push_back({PICKUP , 0});
        sol.push_back({DRIVE , nb[VIDE][M].back()});
        nb[VIDE][M].pop_back();
        sol.push_back({DROPOFF,0});
        rien();
    }
    else if (!fini()) assert(false);
}

void rien()
{
    if (!fini () && need_C() && nb[C][VIDE].size() > 0)
    {
        sol.push_back({DRIVE,nb[C][VIDE].back()});
        nb[C][VIDE].pop_back();
        peutC();
    }
    else if (!fini() && need_M() && nb[M][VIDE].size() > 0)
    {
        sol.push_back({DRIVE,nb[M][VIDE].back()});
        nb[M][VIDE].pop_back();
        peutM();
    }
    else if (!fini()) assert(false);
}
signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int N;
    cin >> N;
    string initial;
    string target;
    cin >> target >> initial;
    for (int i = 0 ; i < N ; i++)
    {
        nb[to_const(initial[i])][to_const(target[i])].push_back(i+1);
    }
    rien();
    cout<<sol.size()<<endl;
    for (auto el : sol)
    {
        if (el.first == PICKUP)
        {
            cout<<"PICKUP"<<endl;
        }
        else if (el.first == DRIVE)
        {
            cout<<"DRIVE"<<" "<<el.second<<endl;
        }
        else
        {
            cout<<"DROPOFF"<<endl;
        }
    }
    

}