#include<bits/stdc++.h>
#define pb push_back
#define sz(x) (int)(x).size()
#define f first
#define s second
#define ll long long
using namespace std;

int main(){
    int n;
    scanf("%i",&n);
    string a,b;
    cin >> a >> b;
    vector<int> free[6];
    vector<int> bf[6];
    vector<int> type(n);
    for(int i=0;i<n;i++){
        if(a[i]==b[i])continue;
        int ind;
        if(a[i]=='-'){
            if(b[i]=='M')ind=1;
            else ind=0;
        }
        if(a[i]=='C'){
            if(b[i]=='-')ind=4;
            else ind=2;
        }
        if(a[i]=='M'){
            if(b[i]=='-')ind=5;
            else ind=3;
        }
        free[ind].pb(i);
        type[i]=ind;
    }
    for(int i=0;i<6;i++)bf[i]=free[i];
    auto bc=[&](int i){
        int a=free[i].back();
        free[i].pop_back();
        return a;
    };
    for(int o=0;o<2;o++)for(int o2=0;o2<2;o2++){for(int k=-1;;k++){
    for(int i=0;i<6;i++)free[i]=bf[i];
    vector<int> path;
    vector<vector<int>> paths;
    if(k!=-1){
    if(o){
        if(sz(free[2])==0)break;
        path.pb(bc(2));
        bool bad=0;
        for(int i=0;i<k;i++){
            if(sz(free[2])==0||sz(free[3])==0){
                bad=1;
                break;
            }
            path.pb(bc(3));
            path.pb(bc(2));
        }
        if(bad)break;
        if(o2){
            if(sz(free[3])==0)break;
            path.pb(bc(3));
        }
    }
    else{
        if(sz(free[3])==0)break;
        path.pb(bc(3));
        bool bad=0;
        for(int i=0;i<k;i++){
            if(sz(free[2])==0||sz(free[3])==0){
                bad=1;
                break;
            }
            path.pb(bc(2));
            path.pb(bc(3));
        }
        if(bad)break;
        if(o2){
            if(sz(free[2])==0)break;
            path.pb(bc(2));
        }
    }
    }
    while(sz(free[4])){
        if(sz(free[3])){
            paths.pb({bc(4),bc(3)});
        }
        else{
            if(sz(path)&&type[path[0]]==3){
                vector<int> x;
                x.pb(bc(4));
                for(auto p:path)x.pb(p);
                path=x;
            }
            else
            paths.pb({bc(4)});
        }
    }
    while(sz(free[3])){
        paths.pb({bc(3)});
    }
    while(sz(free[5])){
        if(sz(free[2])){
            paths.pb({bc(5),bc(2)});
        }
        else{
            if(sz(path)&&type[path[0]]==2){
                vector<int> x;
                x.pb(bc(5));
                for(auto p:path)x.pb(p);
                path=x;
            }
            else
            paths.pb({bc(5)});
        }
    }
    while(sz(free[2])){
        paths.pb({bc(2)});
    }
    if(sz(path))
    paths.pb(path);
    bool ok=1;
    for(auto &p:paths){
        if(type[p.back()]==2||type[p.back()]==4){
            if(sz(free[0])==0){
                ok=0;
                break;
            }
            p.pb(bc(0));
        }
        else{
            if(sz(free[1])==0){
                ok=0;
                break;
            }
            p.pb(bc(1));
        }
    }
    if(!ok)continue;
    vector<pair<int,int>> ops;
    bool carry=0;
    for(auto p:paths){
        reverse(p.begin(),p.end());
        for(auto d:p){
            ops.pb({0,d+1});
            if(carry){
                ops.pb({1,0});
            }
            if(b[d]=='-'){
                carry=0;
            }
            else{
                carry=1;
                ops.pb({2,0});
            }
        }
    }
    if(sz(ops)&&ops.back().f==2)ops.pop_back();
    printf("%i\n",sz(ops));
    for(auto p:ops){
        if(p.f==0){
            printf("DRIVE %i\n",p.s);
        }
        if(p.f==1)printf("DROPOFF\n");
        if(p.f==2)printf("PICKUP\n");
    }
    return 0;
    }}
}