#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<vector<int>> paths[6];
    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);
    }
    auto bc=[&](int i){
        int a=free[i].back();
        free[i].pop_back();
        return a;
    };
    while(sz(free[3])&&sz(free[4])){
        int a=bc(3),b=bc(4);
        paths[3].pb({b,a});
    }
    while(sz(free[2])&&sz(free[5])){
        int a=bc(2),b=bc(5);
        paths[2].pb({b,a});
    }
    bool canChose=0;
    if(sz(free[2])&&sz(free[2])==sz(free[3])&&!sz(paths[2])&&!sz(paths[3])){
        canChose=1;
    }
    if(!canChose){
        while(sz(free[2])&&sz(free[3])){
            int a=bc(2),b=bc(3);
            if(sz(paths[2])){
                paths[2][0].pb(b);
                paths[2][0].pb(a);
                continue;
            }
            if(sz(paths[3])){
                paths[3][0].pb(a);
                paths[3][0].pb(b);
                continue;
            }
            if(sz(free[2])&&sz(free[2])>sz(free[3])){
                int x=bc(2);
                paths[2].pb({a,b,x});
                continue;
            }
            if(sz(free[3])){
                int x=bc(3);
                paths[3].pb({b,a,x});
                continue;
            }
        }
        for(auto p:free[2])paths[2].pb({p});
        for(auto p:free[3])paths[3].pb({p});
    }
    while(sz(free[4])){
        paths[2].pb({bc(4)});
    }
    while(sz(free[5])){
        paths[3].pb({bc(5)});
    }
    for(auto &p:paths[2]){
        assert(sz(free[0]));
        p.pb(bc(0));
    }
    for(auto &p:paths[3]){
        assert(sz(free[1]));
        p.pb(bc(1));
    }
    if(canChose){
        assert(sz(free[0])||sz(free[1]));
        if(sz(free[0])){
            vector<int> path;
            for(int i=0;i<sz(free[2]);i++){
                path.pb(free[2][i]);
                path.pb(free[3][i]);
            }
            path.pb(bc(0));
            paths[3].pb(path);
        }
        else{
            vector<int> path;
            for(int i=0;i<sz(free[2]);i++){
                path.pb(free[3][i]);
                path.pb(free[2][i]);
            }
            path.pb(bc(1));
            paths[2].pb(path);
        }
    }
    vector<pair<int,int>> ops;
    bool carry=0;
    for(auto p:paths[2]){
        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});
            }
        }
    }
    for(auto p:paths[3]){
        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");
    }
}