#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;


int main(){
    int n;
    cin>>n;
    string prof;
    string budova;
    cin>>budova;
    cin>>prof;
    char current = '-';
    vector<pair<char,int>> instructions;
    vector<int> beginC;
    vector<int> beginM;
    vector<int> endC;
    vector<int> endM;
    vector<int> swapCforM;
    vector<int> swapMforC;
    for(int i=0;i<n;i++){
        if (prof[i]=='C' && budova[i]=='-'){
            beginC.push_back(i);
        } else if (prof[i]=='M' && budova[i]=='-'){
            beginM.push_back(i);
        } else if (prof[i]=='-' && budova[i]=='C'){
            endC.push_back(i);
        } else if (prof[i]=='-' && budova[i]=='M'){
            endM.push_back(i);
        } else if (prof[i]=='C' && budova[i]=='M'){
            swapCforM.push_back(i);
        } else if (prof[i]=='M' && budova[i]=='C'){
            swapMforC.push_back(i);
        }
    }
    while(true){
        if (current == '-'){
            if (beginC.size()>0 && (!swapMforC.empty() || !endC.empty())){
                current='C';
                instructions.push_back(pair<char,int>('d',*beginC.rbegin()));
                instructions.push_back(pair<char,int>('p',0));
                beginC.pop_back();
                continue;
            }
            if (beginM.size()>0 && (!swapCforM.empty() || !endM.empty())){
                current='M';
                instructions.push_back(pair<char,int>('d',*beginM.rbegin()));
                instructions.push_back(pair<char,int>('p',0));
                beginM.pop_back();
                continue;
            }
        }
        if (current == 'C') {
            if (swapMforC.size()>0){
                current='-';
                instructions.push_back(pair<char,int>('d',*swapMforC.rbegin()));
                instructions.push_back(pair<char,int>('o',0));
                if ((!swapCforM.empty() || !endM.empty())) {
                    instructions.push_back(pair<char,int>('p',0));
                    current='M';
                }
                swapMforC.pop_back();
                continue;
            }
            if (endC.size()>0){
                current='-';
                instructions.push_back(pair<char,int>('d',*endC.rbegin()));
                instructions.push_back(pair<char,int>('o',0));
                endC.pop_back();
                continue;
            }
        }
        if (current == 'M') {
            if (swapCforM.size()>0){
                current='-';
                instructions.push_back(pair<char,int>('d',*swapCforM.rbegin()));
                instructions.push_back(pair<char,int>('o',0));
                if ((!swapMforC.empty() || !endC.empty())) {
                    instructions.push_back(pair<char,int>('p',0));
                    current='C';
                }
                swapCforM.pop_back();
                continue;
            }
            if (endM.size()>0){
                current='-';
                instructions.push_back(pair<char,int>('d',*endM.rbegin()));
                instructions.push_back(pair<char,int>('o',0));
                endM.pop_back();
                continue;
            }
        }
        break;
    }
    cout<<instructions.size()<<'\n';
    for(auto i:instructions){
        if (i.first == 'd') {
            cout<<"DRIVE "<<i.second+1<<'\n';
        }
        if (i.first == 'p') {
            cout<<"PICKUP\n";
        }
        if (i.first == 'o') {
            cout<<"DROPOFF\n";
        }
    }
}