#include <bits/stdc++.h>
using namespace std;

using ll = long long;
const ll INF = 1e18;
template<typename T> 
using graph = vector<multiset<T>>;
int n;
const int N = 3000;
int used[N];
int cnt[N];
graph<int> g(N);
int cur = 0;
string s;
string t;
vector<pair<string, int>> ans;
vector<int>res;
void dfs(int v) {
    auto x = g[v];
    for (int to: x) {
        if(g[v].find(to)!=g[v].end())
        {
            g[v].erase(g[v].find(to));
            dfs(to);
        }

    }
    res.push_back(v);
}

void solve() {
    cin >> n;
    cin >> s >> t;
    map<char, int> mp;
    for (int i = 0; i < n; i++) {
        if (s[i] == t[i])   continue;
        mp[s[i]]++;
        mp[t[i]]--;
    }
    for (int i = 0; i < n; i++) {
        if (s[i] == t[i])   continue;
        if (mp[t[i]] < 0) {
            mp[t[i]]++;
            t[i] = '-';
        }
        if (s[i] == '-')
            g[0].insert(i + 3);
        if (s[i] == 'C')
            g[1].insert(i + 3);
        if (s[i] == 'M')
            g[2].insert(i + 3);
    
        if (t[i] == '-')
            g[i + 3].insert(0);
        if (t[i] == 'C')
            g[i + 3].insert(1);
        if (t[i] == 'M')
            g[i + 3].insert(2);
    }
    cnt[0] = g[0].size();
    cnt[1] = g[1].size();
    cnt[2] = g[2].size();
    dfs(0);
    reverse(res.begin(), res.end());
    int cur = 0;
    for (auto i : res) {
        if (i <= 2)
            continue;
        ans.push_back({"DRIVE", i - 2});

        if (cur) {
            ans.push_back({"DROPOFF", -1});
            cur--;
        }
        if (t[i - 3] != '-') {
            ans.push_back({"PICKUP", -1});
            cur++;
        }
    }
    // cout<<"------------------"<<endl;
    // for(int i:res)cout<<i<<" ";

    cout << ans.size() << "\n";
    for (auto [s, t]: ans) {
        cout << s;
        if (t != -1)
            cout << " " << t;
        cout << "\n";
    }
}

int32_t main() {
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}