#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
int n;
string s1,s2;
queue <int> q[10];
char koj='.';
vector<pii> ans;

void drive (int i) {
    ans.push_back({i, 0});
}
void pickup() {
    ans.push_back({0, 1});
}
void dropoff() {
    ans.push_back({0, 2});
}
int main() {
    cin>>n>>s1>>s2;
    for(int i=0; i<n; i++){
        if(s1[i]=='-' && s2[i]=='C'){
            q[0].push(i+1);
        }
        if(s1[i]=='C' && s2[i]=='-'){
            q[1].push(i+1);
        }
        if(s1[i]=='-' && s2[i]=='M'){
            q[2].push(i+1);
        }
        if(s1[i]=='M' && s2[i]=='-'){
            q[3].push(i+1);
        }
        if(s1[i]=='C' && s2[i]=='M'){
            q[4].push(i+1);
        }
        if(s1[i]=='M' && s2[i]=='C'){
            q[5].push(i+1);
        }
    }
    while(q[1].size()>0 || q[3].size()>0 || q[4].size()>0 || q[5].size()>0){
        if(koj=='.' && q[0].size()>0){
            drive(q[0].front());
            pickup();
            q[0].pop();
            koj='C';
        }
        else if(koj=='.' && q[2].size()>0){
            drive(q[2].front());
            pickup();
            q[2].pop();
            koj='M';
        }
        else if(koj=='C'){
            if(q[4].size()>0){
                drive(q[4].front());
                dropoff();
                pickup();
                q[4].pop();
                koj='M';
            }
            else if(q[1].size()>0){
                drive(q[1].front());
                dropoff();
                q[1].pop();
                koj='.';
            }
            else{
                drive(q[2].front());
                pickup();
                q[2].pop();
                koj='M';
            }
        }
        else if(koj=='M'){
            if(q[5].size()>0){
                drive(q[5].front());
                dropoff();
                pickup();
                q[5].pop();
                koj='C';
            }
            else if(q[3].size()>0){
                drive(q[3].front());
                dropoff();
                q[3].pop();
                koj='.';
            }
            else{
                drive(q[0].front());
                pickup();
                q[0].pop();
                koj='C';
            }
        }
    }

    cout << ans.size() << "\n";
    for (pii p : ans) {
        if (p.second == 0) {
            cout << "DRIVE " << p.first << "\n";
        } else if (p.second == 1) cout << "PICKUP\n";
        else cout << "DROPOFF\n";
    }

    return 0;
}