#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
#define all(x) begin(x),end(x)
#define rep(i,a,b) for(int i=a;i<b;++i)
#define sz(x) int(x.size())



vi eulerWalk(vector<vector<pi>>& gr, int nedges, int src=0) {
    int n = sz(gr);
    vi D(n), its(n), eu(nedges),ret;
    vector<pi> s={{src,-1}};
    //  D[src]++;
    while(!s.empty()) {
        auto [x,eid] = s.back();
        int y, e, &it = its[x], end = sz(gr[x]);
        if (it==end){ ret.push_back(eid); s.pop_back(); continue;}
        tie(y,e) = gr[x][it++];
        if (!eu[e]) {
            D[x]--, D[y]++;
            eu[e]=1; s.push_back({y,e});
        }
    }
    for (int x:D) if (x<0||sz(ret) != nedges+1) return {};
    return {ret.rbegin(),ret.rend()};

}


int main() {
    int n;
    cin >> n;
    string build;
    string prof;
    cin >> build;
    cin >> prof;

    int d2=0;
    int d3=0;

    // vi stopC;
    // vi sopM;
    vector<pi> edges = {{0,1},{1,0}};
    vector<int> ed = {-2,-2}; //edge's building



    rep(i,0,n) {
        char b=build[i];
        char p=prof[i];

        if (b==p) continue;
        if (b=='-') { // GEN
            if (p=='C') {
                edges.push_back({1,2});
                ed.push_back(i);
                d2++;
            } else if (p=='M') {
                edges.push_back({1,3});
                ed.push_back(i);
                d3++;
            }
        } else if (p=='-') { //STOP
            if (b=='C') {
                edges.push_back({2,1});
                ed.push_back(i);
                d2--; 
                // stopC.push_back(i);
            } else if (b=='M') {
                edges.push_back({3,1});
                ed.push_back(i);
                d3--;
                // stopM.push_back(i);
            }
        } else {
            if (b=='C' && p=='M') {
                edges.push_back({2,3});
                ed.push_back(i);
                d2--; d3++;
            } else if (b=='M' && p=='C') {
                edges.push_back({3,2});
                ed.push_back(i);
                d3--; d2++;
            }
        }
    }

    rep(i,0,d2) {
        edges.push_back({2,1});
        ed.push_back(-1);
    }


    rep(i,0,d3) {
        edges.push_back({3,1});
        ed.push_back(-1);
    }

    vector<vector<pi>> adj(4);
    rep(i,0,sz(edges)){
        adj[edges[i].first].push_back({edges[i].second,i});
    }


    vi path = eulerWalk(adj,sz(edges),0);
    path.erase(path.begin());

    // for (auto p: edges) cout << "// " << p.first << ' ' << p.second << endl;
    int s=0;
    // cout << path.size() << '\n';
        for(int i : path) {
        if (ed[i]<0) continue;
        // if (i==-2) continue;
        
        // (pick up prof for x) drive to building x (drop off prof for x)
        if (build[ed[i]] != '-') {
            s++;
        }

        s++;
        if (build[ed[i]] != '-') {
            s++;
        }
    }
    cout << s << '\n';
    for(int i : path) {
        if (ed[i]<0) continue;
        // if (i==-2) continue;
        
        // (pick up prof for x) drive to building x (drop off prof for x)
        if (build[ed[i]] != '-') {
            cout << "PICKUP\n";
        }

        cout << "DRIVE " << ed[i]+1 << "\n";

        if (build[ed[i]] != '-') {
            cout << "DROPOFF\n";
        }
    }



}

// 3    
// CM-
// -CM

// 0 1
// 1 0
// 2 1
// 1 3
// 3 1


/*
3
CM-
-CM
// 0 1
// 1 0
// 2 1
// 3 2
// 1 3
PICKUP
DRIVE 1
DROPOFF
PICKUP
DRIVE 68
DROPOFF
DRIVE 46
PICKUP
DRIVE 78
DROPOFF
PICKUP
DRIVE 68
DROPOFF


*/
/*
1
C
C
// 0 1
// 1 0
PICKUP
DRIVE 1CM-
-CM
// 0 1
// 1 0
// 2 1
// 3 2
// 1 3
PICKUP
DRIVE -1
DROPOFF
PICKUP
DRIVE 1
DROPOFF
DRIVE 3
PICKUP
DRIVE 2
DROPOFF
PICKUP
DRIVE 1
DROPOFF
DROPOFF
PICKUP
DRIVE 68
DROPOFF
*/

/*
CM-
-CM
// 0 1
// 1 0
// 2 1
// 3 2
// 1 3
PICKUP
DRIVE -1
DROPOFF
PICKUP
DRIVE 1
DROPOFF
DRIVE 3
PICKUP
DRIVE 2
DROPOFF
PICKUP
DRIVE 1
DROPOFF
*/