#pragma GCC optimize ("O3")
#include "bits/stdc++.h"
using namespace std;

#define rep(i, b, e) for(int i = (b); i <= (e); i++)
#define per(i, b, e) for(int i = (e); i >= (b); i--)
#define FOR(i, b, e) rep(i, b, (e) - 1)
#define SZ(x) int(x.size())
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define st first
#define nd second
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

auto &operator<<(auto &o, pair<auto, auto> p) {
    return o << "(" << p.st << ", " << p.nd << ")";
}

auto operator<<(auto &o, auto x)->decltype(end(x), o) {
    o << "{"; int i=0; for(auto e: x) o << ", " + 2*!i++ << e;
    return o << "}";
}

#ifdef LOCAL
#define deb(x...) cerr << "[" #x << "]: ", [](auto...$) { ((cerr << $ << "; "),...) << endl; }(x)
#else
#define deb(...)
#endif

void solve() {
    int n;
    string s[2];
    cin >> n;
    FOR(i, 0, 2) cin >> s[i];
    vector<bool> vis(n);
    vector<pii> ops;    // 0 - drop, 1 - pick, 2 - drive
    FOR(i, 0, n) if(s[0][i] == s[1][i]) vis[i] = 1;
    while(true) {
        int cand = -1;
        FOR(i, 0, n) if(!vis[i] && s[0][i] == '-' && s[1][i] != '-') cand = i;
        if(cand == -1) break;
        vis[cand] = 1;
        ops.pb({2, cand});
        for(int pos = cand; ;) {
            char co = s[1][pos];
            int gst = -1;
            FOR(i, 0, n) if(!vis[i] && s[0][i] == co && s[1][i] != '-') gst = i;
            if(gst != -1) {
                ops.pb({1, -1}); ops.pb({2, gst}); ops.pb({0, -1});
                pos = gst;
                vis[pos] = 1;
                continue;
            }
            FOR(i, 0, n) if(!vis[i] && s[0][i] == co && s[1][i] == '-') gst = i;
            if(gst == -1) break;
            ops.pb({1, -1}); ops.pb({2, gst}); ops.pb({0, -1});
            vis[gst] = 1;
            break;
        }
    }
    cout << SZ(ops) << '\n';
    for(auto &[x, y]: ops) {
        if(x == 0) cout << "DROPOFF\n";
        if(x == 1) cout << "PICKUP\n";
        if(x == 2) cout << "DRIVE " << y + 1 << '\n';
    }
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int tt = 1;
    // cin >> tt;
    FOR(te, 0, tt) solve();
    return 0;
}