#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
using ll=long long;
using pii=pair<int,int>;
using vi=vector<int>;
using vl=vector<ll>;
#define pb push_back
#define all(a) begin(a),end(a)

const int N=300010,MOD=1e9+7;
const char en='\n';
const ll LLINF=1ll<<60;

int n,dif[N];
string a,b;
vector<pair<int,pair<char,char>>> ord;
set<int> s[300][300];

void dfs(char c)
{
	for (auto u: {'-','M','C'}) while (s[c][u].size())
	{
		int x=*s[c][u].begin();
		s[c][u].erase(x);
		dfs(u);
		ord.pb({x,{c,u}});
	}
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin>>n>>a>>b;
	for (int i=0;i<n;++i)
	{
		if (a[i]!=b[i]) s[a[i]][b[i]].insert(i),--dif[a[i]],++dif[b[i]];
	}
	while (dif['M']>0 && s['C']['M'].size())
	{
		int u=*s['C']['M'].begin();
		s['C']['M'].erase(u);
		--dif['M'];
		s['C']['-'].insert(u);
		++dif['-'];
	}
	while (dif['C']>0 && s['M']['C'].size())
	{
		int u=*s['M']['C'].begin();
		s['M']['C'].erase(u);
		--dif['C'];
		s['M']['-'].insert(u);
		++dif['-'];
	}
	while (dif['M']>0 && s['-']['M'].size())
	{
		int u=*s['-']['M'].begin();
		s['-']['M'].erase(u);
		--dif['M'];
	}
	while (dif['C']>0 && s['-']['C'].size())
	{
		int u=*s['-']['C'].begin();
		s['-']['C'].erase(u);
		--dif['C'];
	}
	dfs('-');
	reverse(all(ord));
	vector<pair<string,int>> v;
	for (auto x: ord)
	{
		v.pb({"DRIVE",x.x+1});
		if (x.y.x!='-') v.pb({"DROPOFF",-1});
		if (x.y.y!='-') v.pb({"PICKUP",-1});
	}
	cout<<v.size()<<en;
	for (auto x: v)
	{
		cout<<x.x;
		if (x.y!=-1) cout<<' '<<x.y;
		cout<<en;
	}
}