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

using ll=long long;
//#define int ll
#define rep(i,a,b) for(int i=a;i<(b);i++)
#define sz(x) (int)(x).size()
#define all(x) begin(x), end(x)
using pii=pair<int,int>;
using vi=vector<int>;
#define fi first
#define se second
#define pb push_back
int id(char c) {
    if(c == '-') return 0;
    if(c == 'C') return 1;
    if(c == 'M') return 2;
    assert(0);
}

vi eulerWalk(vector<vector<pii>>&gr, int nedges,int src=0)
{
    int n=sz(gr);
    vi D(n),its(n),eu(nedges),ret,s={src};
//    D[src]++;//
    while(!s.empty())
    {
        int x=s.back(),y,e,&it=its[x],end=sz(gr[x]);
        if(it==end) {ret.push_back(x); s.pop_back();
            continue;}
        tie(y,e)=gr[x][it++];
        if(!eu[e]){
            D[x]--,D[y]++;
            eu[e]=1;s.push_back(y);
        }
    }
    for (int x:D) if(x<0||sz(ret)!=nedges+1) return {};
    return {ret.rbegin(),ret.rend()};
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int n;
    cin >> n;
    string S, P;
//    if(local) {
////        for(auto i : S)
//    } else {
    cin >> S >> P;
//    }

    array<array<int, 3>, 3> cnt;
    vector<vector<vector<int>>> edges(3, vector<vector<int>>(3));
    vector<vector<pii>> g(3);
    int s = 0;
//    int wantM = count(all(S), 'M');
//    int wantC = count(all(S), 'C');
//    for(auto &i : P) {
//        if(i == 'M') {
//            if(wantM) wantM--;
//            else i = '-';
//        }//3 MC- CMM
//        if(i == 'C') {
//            if(wantC) wantC--;
//            else i = '-';
//        }
//    }
    for(auto c : {'M', 'C'}) {
//        cout << c << endl;
        int want = 0;
        for(auto i : S) want -= i == c;
        for(auto i : P) want += i == c;
        for(int i = 0; i < n; i++) {
            if(S[i] == c && P[i] == c && want) {
                want--;
                P[i] = '-';
            }
        }
        for(int i = 0; i < n; i++) {
            if(P[i] == c && want) {
                want--;
                P[i] = '-';
            }
        }
    }
//    cout << S << " " << P << endl;
    for(auto &i : cnt) i.fill(0);
    int KIREKHAR = 0;
    for(int i = 0; i < n; i++) {
        int from = id(S[i]), to = id(P[i]);
        if(from != to) {
            cnt[from][to]++;
            edges[from][to].push_back(i);
            g[from].push_back({to, KIREKHAR++});
//            s = from;
        }
    }
    vector<pair<string, int>> ops;
    auto get = [&](int u, int v) {
        cnt[u][v]--;
        int t = edges[u][v].back();
        edges[u][v].pop_back();
        return t;
    };
    auto do_edge = [&](int x, int y) -> void {
        ops.push_back({"DRIVE", get(x, y)});
        if(x) ops.push_back({"DROPOFF", 0});
        if(y) ops.push_back({"PICKUP", 0});
    };

    auto ord = eulerWalk(g, KIREKHAR, 0);
//    cout << ord.size() << " " << KIREKHAR << endl;
    for(int i = 1; i <= KIREKHAR; i++) {
        do_edge(ord[i - 1], ord[i]);
    }


    for(auto &i : cnt) for(auto &j : i) assert(!j);
    cout << ops.size() << '\n';
    for(auto [s, t] : ops) {
        cout << s;
        if(s == "DRIVE") {
            cout << " " << 1+t << '\n';
        } else cout << '\n';
    }
}