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

#define fi first
#define se second
#define mp make_pair
#define pb push_back
typedef pair<int, int> ii;

const int len = 2005;
char cl[len], pr[len];
vector<int> vec[3][2], out;

bool check(int cur) {
    return (vec[cur][0].size() > 0 || vec[cur][1].size() > 0);
}

int main() {
    int n;
    scanf("%d %s %s", &n, &cl, &pr);

    int math = 0, cs = 0, some = 0;
    for (int i = 0; i < n; i++) {
        if (cl[i] == 'M' && pr[i] != 'M') {
            some++;
            math++;
            if (pr[i] == 'C')
                cs--, vec[0][1].pb(i+1);
            else
                vec[0][0].pb(i+1);
        }
        else if (cl[i] == 'C' && pr[i] != 'C') {
            some++;
            cs++;
            if (pr[i] == 'M')
                math--, vec[1][0].pb(i+1);
            else
                vec[1][1].pb(i+1);
        }
    }

    //printf("%d %d\n", math, cs);
    //printf("some = %d\n", some);

    if (some == 0) {
    }
    else if (some > 0 && math == 0 && cs == 0) {
        for (int i = 0; i < n; i++) {
            if (cl[i] == '-' && pr[i] == 'M') {
                vec[2][0].pb(i+1);
                break;
            }
            else if (cl[i] == '-' && pr[i] == 'C') {
                vec[2][1].pb(i+1);
                break;
            }
        }
    }
    else {
        math = max(math, 0);
        cs = max(cs, 0);
        for (int i = 0; i < n; i++) {
            if (cl[i] == '-' && pr[i] != '-') {
                if (pr[i] == 'M' && math > 0)
                    math--, vec[2][0].pb(i+1);
                else if (pr[i] == 'C' && cs > 0)
                    cs--, vec[2][1].pb(i+1);
            }
        }
    }


    int cur = 2;
    while (true) {
        //printf("cur = %d\n", cur);
        if (cur == 2) {
            if (vec[2][0].size() > 0) {
                out.pb(vec[2][0].back());
                out.pb(-2);

                cur = 0;
                vec[2][0].pop_back();
            }
            else if (vec[2][1].size() > 0) {
                out.pb(vec[2][1].back());
                out.pb(-2);

                cur = 1;
                vec[2][1].pop_back();
            }
            else {
                break;
            }
        }
        else {
            if (vec[cur][1-cur].size() > 0) {
                out.pb(vec[cur][1-cur].back());
                out.pb(-3);
                vec[cur][1-cur].pop_back();

                if (check(1-cur))
                    out.pb(-2), cur = 1-cur;
                else
                    cur = 2;
            }
            else {
                out.pb(vec[cur][cur].back());
                out.pb(-3);

                vec[cur][cur].pop_back();
                cur = 2;
            }
        }
    }

    printf("%d\n", out.size());
    for (int v: out) {
        if (v == -2) printf("PICKUP\n");
        else if (v == -3) printf("DROPOFF\n");
        else printf("DRIVE %d\n", v);
    }
    return 0;
}