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

using ll = long long int;
using ld = long double;
#define N 2010
#define pii pair<int,int>
#define mk make_pair

int n;
char building[N], prof[N];
vector<int> acc[2], confli[2], have[2]; // 0 for cs 1 for math
vector<int> res;

int pop_back_get(vector<int>& vec) {
    int res = *vec.rbegin();
    vec.pop_back();
    return res;
}

bool need_sub(int sub) {
    return acc[0].size() + confli[0].size() > 0;
}

int need() {
    if(confli[0].size() > confli[1].size()) return 0;
    if(confli[1].size() > confli[0].size()) return 0;
    if(confli[0].size() > 0) return 0;
    if(confli[1].size() > 0) return 1;
    if(need_sub(0)) return 0;
    else if(need_sub(1)) return 1;
    else return -1;
}

int get(int sub) {
    if(have[sub].empty()) return -1;
    return pop_back_get(have[sub]);
}

int give(int sub) {
    if(confli[sub].empty()) {
        if(acc[sub].empty()) return -1;
        return pop_back_get(acc[sub]);
    } else {
        return pop_back_get(confli[sub]);
    }
}

int main(void) {
    ios_base::sync_with_stdio(false);
    cin >> n >> building >> prof;
    for(int i=0;i<n;++i) {
        if(building[i] == '-') {
            if(prof[i] == 'C') {
                have[0].push_back(i);
            } else if(prof[i] == 'M') {
                have[1].push_back(i);
            }
        } else if(building[i] == 'C') {
            if(prof[i] == '-') {
                acc[0].push_back(i);
            } else if(prof[i] == 'M') {
                confli[0].push_back(i);
            }
        } else if(building[i] == 'M') {
            if(prof[i] == '-') {
                acc[1].push_back(i);
            } else if(prof[i] == 'C') {
                confli[1].push_back(i);
            }
        }
    }

    int cur = -1, ondrive;
    while(need() != -1) {
        // cerr <<cur<<endl;
        if(cur != -1 && prof[cur] != '-')
            ondrive = (prof[cur] == 'M');
        else ondrive = -1;
        if(ondrive != -1 && need_sub(ondrive)) {
            res.push_back(-1);
            cur = give(ondrive);
            res.push_back(cur);
            res.push_back(-2);
        } else {
            cur = get(ondrive = need());
            res.push_back(cur);
            res.push_back(-1); // -1 for pick up
            cur = give(ondrive);
            // cerr << cur << "," << ondrive << endl;
            // return 0;
            res.push_back(cur);
            res.push_back(-2); // -2 for drop
        }
    }
    cout << res.size() << endl;
    for(int s : res) {
        if(s == -1) {
            cout << "PICKUP\n";
        } else if(s == -2) {
            cout << "DROPOFF\n";
        } else {
            cout << "DRIVE " << s+1 << "\n";
        }
    }
    return 0;
}