#include <iostream>
#include <bits/stdc++.h>

using namespace std;
typedef long long int ll;

int main() {
    ll n;
    cin >> n;
    string b, p;
    cin >> b >> p;
    vector<ll> needMhasC, needChasM, hasC, hasM, needC, needM;
    ll needMhasCPos = 0, needChasMPos = 0, hasCPos = 0, hasMPos = 0, needCPos = 0, needMPos = 0;
    vector<string> ans;

    for (ll i = 0; i < n; ++i) {
        if (b[i] == 'C' && p[i] == 'M') needChasM.emplace_back(i);
        if (b[i] == 'M' && p[i] == 'C') needMhasC.emplace_back(i);
        if (b[i] == '-' && p[i] == 'C') hasC.emplace_back(i);
        if (b[i] == '-' && p[i] == 'M') hasM.emplace_back(i);
        if (b[i] == 'C' && p[i] == '-') needC.emplace_back(i);
        if (b[i] == 'M' && p[i] == '-') needM.emplace_back(i);
    }

    ll curType = 0;
    bool started = false;
    bool hasMath = false;
    bool loaded = false;
    while (needMhasC.size() != needMhasCPos || needChasM.size() != needChasMPos || hasC.size() != hasCPos ||
           hasM.size() != hasMPos || needC.size() != needCPos || needM.size() != needMPos) {
        if (!started) {
            if (hasMPos != hasM.size()) {
                started = true;
                if (loaded)
                    ans.emplace_back("DROPOFF");
                ans.emplace_back("DRIVE " + to_string(hasM[hasMPos] + 1));
                ans.emplace_back("PICKUP");
                hasMPos++;
                hasMath = true;
                loaded = true;
                continue;
            }

            if (hasCPos != hasC.size()) {
                started = true;
                if (loaded)
                    ans.emplace_back("DROPOFF");
                ans.emplace_back("DRIVE " + to_string(hasC[hasCPos] + 1));
                ans.emplace_back("PICKUP");
                hasCPos++;
                hasMath = false;
                loaded = true;
                continue;
            }
        } else {
            if (hasMath) {
                if (needMhasC.size() != needMhasCPos) {
                    ans.emplace_back("DRIVE " + to_string(needMhasC[needMhasCPos] + 1));
                    ans.emplace_back("DROPOFF");
                    ans.emplace_back("PICKUP");
                    needMhasCPos++;
                    hasMath = false;
                    continue;
                }
                if (needM.size() != needMPos) {
                    ans.emplace_back("DRIVE " + to_string(needM[needMPos] + 1));
                    ans.emplace_back("DROPOFF");
                    needMPos++;
                    loaded = false;
                    started = false;
                    continue;
                }
            } else {
                if (needChasM.size() != needChasMPos) {
                    ans.emplace_back("DRIVE " + to_string(needChasM[needChasMPos] + 1));
                    ans.emplace_back("DROPOFF");
                    ans.emplace_back("PICKUP");
                    needChasMPos++;
                    hasMath = true;
                    continue;
                }
                if (needC.size() != needCPos) {
                    ans.emplace_back("DRIVE " + to_string(needC[needCPos] + 1));
                    ans.emplace_back("DROPOFF");
                    needCPos++;
                    loaded = false;
                    started = false;
                    continue;
                }
            }
        }
    }
    ll x = ans.size();
    for (int i = ans.size() - 1; i >= 0; --i) {
        if (ans[i] == "DROPOFF") {
            x = i + 1;
            break;
        }
    }
    cout << x << endl;
    for (int i = 0; i < x; ++i) {
        cout << ans[i] << endl;
    }

    return 0;
}