#include<bits/stdc++.h>

using namespace std;

vector<string> ans;

void f(vector<int> &C, vector<int> &CM, vector<int> &M, vector<int> &MC, vector<int> &_M, vector<int> &_C){
	while(C.size()){
		ans.push_back("DRIVE " + to_string(C.back()));
		ans.push_back("PICKUP");
		C.pop_back();
		bool w = 0;
		while(true){
			if(MC.size()){
				ans.push_back("DRIVE " + to_string(MC.back()));
				ans.push_back("DROPOFF");
				ans.push_back("PICKUP");
				MC.pop_back();
				w = 1;
			}
			else break;
			if(CM.size()){
				ans.push_back("DRIVE " + to_string(CM.back()));
				ans.push_back("DROPOFF");
				ans.push_back("PICKUP");
				CM.pop_back();
				w = 0;
			}
			else break;
		}
		if(!w){
			if(_C.size()){
				ans.push_back("DRIVE " + to_string(_C.back()));
				ans.push_back("DROPOFF");
				_C.pop_back();
			}
			else{
				ans.pop_back();
			}
		}
		else{
			if(_M.size()){
				ans.push_back("DRIVE " + to_string(_M.back()));
				ans.push_back("DROPOFF");
				_M.pop_back();
			}
			else{
				ans.pop_back();
			}
		}
	}
}

int main(){
	ios_base::sync_with_stdio(0); cin.tie(0);
	int n; cin >> n;
	vector<int> C, CM, M, MC, _M, _C;
	string s; cin >> s;
	string t; cin >> t;
	swap(s, t);
	for(int i = 0; i < n; ++i){
		if(s[i] == t[i])continue;
		if(s[i] == 'C' && t[i] == '-')C.push_back(i + 1);
		if(s[i] == 'C' && t[i] == 'M')CM.push_back(i + 1);
		if(s[i] == 'M' && t[i] == '-')M.push_back(i + 1);
		if(s[i] == 'M' && t[i] == 'C')MC.push_back(i + 1);
		if(s[i] == '-' && t[i] == 'C')_C.push_back(i + 1);
		if(s[i] == '-' && t[i] == 'M')_M.push_back(i + 1);
	}

	f(C, CM, M, MC, _M, _C);
	f(M, MC, C, CM, _C, _M);
	cout << ans.size() << '\n';
	for(auto x : ans)cout << x << '\n';
}