#include <iostream>
#include <bits/stdc++.h>

using namespace std;
typedef long long int ll;

vector<string> result;
vector<int> v_c, v_m, mc, cm, m_, c_;

void pickC();
void pickM();

void pickC(){
    if (!cm.empty()){
        int v = cm.back();
        cm.pop_back();
        result.emplace_back("DROPOFF");
        result.push_back("DRIVE " + to_string(v +1));
        result.emplace_back("PICKUP");
        pickM();
    }
    else if (!c_.empty()) {
        int v = c_.back();
        c_.pop_back();
        result.push_back("DRIVE " + to_string(v +1));
        //result.emplace_back("PICKUP");
    }
    else throw std::runtime_error("unreachable");
}

void pickM(){
    if (!mc.empty()){
        int v = mc.back();
        mc.pop_back();
        result.emplace_back("DROPOFF");
        result.push_back("DRIVE " + to_string(v +1));
        result.emplace_back("PICKUP");
        pickC();
    }
    else if (!m_.empty()) {
        int v = m_.back();
        m_.pop_back();
        result.push_back("DRIVE " + to_string(v +1));
        //result.emplace_back("PICKUP");
    }
    else throw std::runtime_error("unreachable");
}

int main(){
    int n;
    cin >> n;
    string sHave, sWant;
    cin >> sWant >> sHave;
    for (int i=0; i<n; i++){
        if (sHave[i] == '-' && sWant[i] == 'C'){
            v_c.push_back(i);
        }
        if (sHave[i] == '-' && sWant[i] == 'M'){
            v_m.push_back(i);
        }
        if (sHave[i] == 'M' && sWant[i] == 'C'){
            mc.push_back(i);
        }
        if (sHave[i] == 'C' && sWant[i] == 'M'){
            cm.push_back(i);
        }
        if (sHave[i] == 'M' && sWant[i] == '-'){
            m_.push_back(i);
        }
        if (sHave[i] == 'C' && sWant[i] == '-'){
            c_.push_back(i);
        }
    }
    while (!v_m.empty()){
        int v = v_m.back();
        v_m.pop_back();
        result.emplace_back("DROPOFF");
        result.push_back("DRIVE " + to_string(v+1));
        result.emplace_back("PICKUP");
        pickM();
    }
    while (!v_c.empty()){
        int v = v_c.back();
        v_c.pop_back();
        result.emplace_back("DROPOFF");
        result.push_back("DRIVE " + to_string(v+1));
        result.emplace_back("PICKUP");
        pickC();
    }
    while (!cm.empty()){
        int v = cm.back();
        cm.pop_back();
        result.emplace_back("DROPOFF");
        result.push_back("DRIVE " + to_string(v+1));
        result.emplace_back("PICKUP");
        pickM();
    }
    while (!mc.empty()){
        int v = mc.back();
        mc.pop_back();
        result.emplace_back("DROPOFF");
        result.push_back("DRIVE " + to_string(v+1));
        result.emplace_back("PICKUP");
        pickC();
    }
    cout << result.size() << '\n';
    for (int i=int(result.size()) - 1;i>=0;i--){
        cout << result[i] << '\n';
    }
    
}