#include<bits/stdc++.h>

using namespace std;

#define int long long
#define double long double
#define vi vector<int>
#define vvi vector<vi>

#define pii pair<int,int>
#define piii pair<pii,int>
#define viii vector<piii>
#define vii vector<pii>

#define fi first
#define se second

#define pb push_back
const double eps=1e-12;

vector<string> orders;

void drive(int x){
    orders.pb(string("DRIVE " +to_string(x)));
}
void pick(){
    orders.pb("PICKUP");
}
void drop(){
    if (orders.back()=="PICKUP") orders.pop_back();
    else orders.pb("DROPOFF");
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    int n;
    cin >> n;
    string s1,s2;
    cin >> s1 >> s2;

    vi cm,mc,c_,_c,m_,_m;
    for (int i=0;i<n;i++){
        if (s1[i]=='C' && s2[i]=='M') cm.pb(i+1);
        if (s1[i]=='M' && s2[i]=='C') mc.pb(i+1);
        if (s1[i]=='C' && s2[i]=='-') c_.pb(i+1);
        if (s1[i]=='-' && s2[i]=='C') _c.pb(i+1);
        if (s1[i]=='M' && s2[i]=='-') m_.pb(i+1);
        if (s1[i]=='-' && s2[i]=='M') _m.pb(i+1);
    }

    while (_c.size() || _m.size()){
        char ac;
        if (_c.size()){
            drive(_c.back());
            pick();
            _c.pop_back();
            ac='C';
        }
        else{
            drive(_m.back());
            pick();
            _m.pop_back();
            ac='M';
        }

        while (ac!='-'){
            if (ac=='C'){
                if (cm.size()){
                    drive(cm.back());
                    drop();
                    pick();
                    cm.pop_back();
                    ac='M';
                }
                else if (c_.size()){ // c-
                    drive(c_.back());
                    drop();
                    c_.pop_back();
                    ac='-';
                }
                else{
                    drop();
                    ac='-';
                }
            }
            else{
                if (mc.size()){
                    drive(mc.back());
                    drop();
                    pick();
                    mc.pop_back();
                    ac='C';
                }
                else if (m_.size()){ // c-
                    drive(m_.back());
                    drop();
                    m_.pop_back();
                    ac='-';
                }
                else{
                    drop();
                    ac='-';
                }
            }
        }
    }

    cout << orders.size() << '\n';
    for (string s:orders) cout << s << "\n";
}