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

#define Dv(v) for (auto x : v) cerr << x << ' '; cerr << endl;
#define D(x) cerr << #x << " = " << x << ", "

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    string needs, has;
    cin >> needs >> has;
    vector<int> mc, cm, mx, cx, xm, xc;
    for (int i = 1; i <= n; ++i) {
        if (needs[i-1] == 'M' && has[i-1] == 'C') {
            mc.push_back(i);
        } else if (needs[i-1] == 'C' && has[i-1] == 'M') {
            cm.push_back(i);
        } else if (needs[i-1] == 'C' && has[i-1] == '-') {
            cx.push_back(i);
        } else if (needs[i-1] == 'M' && has[i-1] == '-') {
            mx.push_back(i);
        } else if (needs[i-1] == '-' && has[i-1] == 'M') {
            xm.push_back(i);
        } else if (needs[i-1] == '-' && has[i-1] == 'C') {
            xc.push_back(i);
        }
    }
    vector<pair<string, int>> ans;
    char holding = '-';
    while (!mc.empty() || !cm.empty() || !mx.empty() || !cx.empty()) {
        if (holding == '-') {
            if ((!mc.empty() || !mx.empty()) && !xm.empty()) {
                ans.push_back({"DRIVE ", xm.back()});
                ans.push_back({"PICKUP", 0});
                holding = 'M';
                xm.pop_back();
            } else {
                assert(!xc.empty());
                ans.push_back({"DRIVE ", xc.back()});
                ans.push_back({"PICKUP", 0});
                holding = 'C';
                xc.pop_back();
            }
        } else if (holding == 'C') {
            if (!cm.empty()) {
                ans.push_back({"DRIVE ", cm.back()});
                ans.push_back({"DROPOFF", 0});
                if (!mc.empty() || !mx.empty()){
                    ans.push_back({"PICKUP", 0});
                    holding = 'M';
                } else {
                    holding = '-';
                }
                cm.pop_back();
            } else {
                assert(!cx.empty());
                ans.push_back({"DRIVE ", cx.back()});
                ans.push_back({"DROPOFF", 0});
                holding = '-';
                cx.pop_back();
            }
        } else {
            assert(holding == 'M');
            if (!mc.empty()) {
                ans.push_back({"DRIVE ", mc.back()});
                ans.push_back({"DROPOFF", 0});
                if (!cm.empty() || !cx.empty()) {
                    ans.push_back({"PICKUP", 0});
                    holding = 'C';
                } else {
                    holding = '-';
                }
                mc.pop_back();
            } else {
                assert(!mx.empty());
                ans.push_back({"DRIVE ", mx.back()});
                ans.push_back({"DROPOFF", 0});
                holding = '-';
                mx.pop_back();
            }
        }
    }
    cout << ans.size() << '\n';
    for (auto [s, k] : ans) {
        cout << s;
        if (k) cout << k;
        cout << '\n';
    }
}