#include <bits/stdc++.h>

using namespace std;
using ll = long long;

array<array<int, 3>, 3> tp = {{
    {-1, 4, 1}, 
    {3, -1, 2},
    {5, 6, -1}
}};

vector<vector<int>> building(7, vector<int>());
stringstream ss;
int instr = 0;
int stop = -1;
bool passenger = false;

void drive(int t){
    ss << "DRIVE " << building[t].back() << "\n";
    // printf("DRIVE %d\n", building[t].back());
    building[t].pop_back();
    stop = t;
    instr++;
}

void pickup(){
    // printf("PICKUP\n");
    ss << "PICKUP"<< "\n";
    assert(!passenger);
    passenger = true;
    instr++;
}

void dropoff(){
    // printf("DROPOFF\n");
    ss << "DROPOFF"<< "\n";
    assert(passenger);
    passenger = false;
    instr++;
}

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

    int n;
    cin >> n;
    string clas;
    cin >> clas;
    string prof;
    cin >> prof;
    //cout << "lol " << " " << clas.size() << " " << prof.size() << endl;

    for(int i = 0; i < n; ++i) {
        int a = -1, b = -1;
        if(prof[i] == 'M'){
            a = 0;
        }else if(prof[i] == 'C'){
            a = 1;
        }else if(prof[i] == '-'){
            a = 2;
        }
        if(clas[i] == 'M'){
            b = 0;
        }else if(clas[i] == 'C'){
            b = 1;
        }else if(clas[i] == '-'){
            b = 2;
        }
        //cout << a << " " << b << endl;
        if(tp[a][b] == -1) continue;
        building[tp[a][b]].push_back(i + 1);
    }

    if(building[6].size() >= building[5].size()){
    while(building[1].size() > 0 && (building[3].size() > 0 || building[5].size() > 0)){
        drive(1);
        if(passenger) dropoff();
        pickup();
        while(building[3].size() > 0){
            drive(3);
            dropoff();
            pickup();
            if(building[4].size() > 0){
                drive(4);
                dropoff();
                pickup();
            }
        }
        if(stop == 1 || stop == 4){
            if(building[5].size() > 0){
                drive(5);
                dropoff();
            }
        }else if(stop == 3){
            if(building[6].size() > 0){
                drive(6);
                dropoff();
            }
        }
    }

    while(building[2].size() > 0 && (building[4].size() > 0 || building[6].size() > 0)){
        drive(2);
        if(passenger) dropoff();
        pickup();
        if(building[4].size() > 0){
            drive(4);
            dropoff();
            if(building[5].size() > 0){
                pickup();
                drive(5);
                dropoff();
                pickup();
            }
        }else if(building[6].size() > 0){
            drive(6);
            dropoff();
        }
    }
    while(building[1].size() > 0 && building[5].size() > 0){
        drive(1);
        if(passenger) dropoff();
        pickup();
        drive(5);
        dropoff();
    }
    }else{
        while(building[2].size() > 0 && (building[4].size() > 0 || building[6].size() > 0)){
        drive(2);
        if(passenger) dropoff();
        pickup();
        while(building[4].size() > 0){
            drive(4);
            dropoff();
            pickup();
            if(building[3].size() > 0){
                drive(3);
                dropoff();
                pickup();
            }
        }
        if(stop == 2 || stop == 3){
            if(building[6].size() > 0){
                drive(6);
                dropoff();
            }
        }else if(stop == 4){
            if(building[5].size() > 0){
                drive(5);
                dropoff();
            }
        }
    }

    while(building[1].size() > 0 && (building[3].size() > 0 || building[5].size() > 0)){
        drive(1);
        if(passenger) dropoff();
        pickup();
        if(building[3].size() > 0){
            drive(3);
            dropoff();
            if(building[6].size() > 0){
                pickup();
                drive(6);
                dropoff();
                pickup();
            }
        }else if(building[5].size() > 0){
            drive(5);
            dropoff();
        }
    }
    while(building[2].size() > 0 && building[6].size() > 0){
        drive(2);
        if(passenger) dropoff();
        pickup();
        drive(6);
        dropoff();
    }
    }
    if(passenger) dropoff();

    cout << instr << "\n";
    cout << ss.str();
}