#pragma GCC optimize "O3"
#include<bits/stdc++.h>
using namespace std;
using LL=long long;
#define FOR(i,l,r) for(int i=(l);i<=(r);++i)
#define REP(i,n) FOR(i,0,(n)-1)
#define ssize(x) int(x.size())
#ifdef DEBUG
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(x...) cerr<<"["#x"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(x)
#else
#define debug(...) {}
#endif

int main() {
	cin.tie(0)->sync_with_stdio(0);

	int n;
	cin >> n;
	vector<int> is(n), should(n);
	REP(i, n) {
		char x;
		cin >> x;
		if (x == '-')
			should[i] = 0;
		else if (x == 'C')
			should[i] = 1;
		else if (x == 'M')
			should[i] = 2;
		else
			assert(false);
	}
	REP(i, n) {
		char x;
		cin >> x;
		if (x == '-')
			is[i] = 0;
		else if (x == 'C')
			is[i] = 1;
		else if (x == 'M')
			is[i] = 2;
		else
			assert(false);
	}
	debug(n, is, should);
	vector v(3, vector (3, vector<int>{}));
	REP(i, n) {
		v[is[i]][should[i]].emplace_back(i);
	}
	debug(v);

	vector<pair<int, int>> ans;

	int have = 0;

	while (true) {
		if (have == 0) {
			if (ssize(v[1][0])) {
				auto x = v[1][0].back();
				v[1][0].pop_back();
				ans.emplace_back(0, x);
				ans.emplace_back(1, 0);
				have = 1;
			}
			else if (ssize(v[2][0])) {
				auto x = v[2][0].back();
				v[2][0].pop_back();
				ans.emplace_back(0, x);
				ans.emplace_back(1, 0);
				have = 2;
			}
			else {
				break;
			}
		}
		else if (have == 1) {
			if (ssize(v[2][1])) {
				auto x = v[2][1].back();
				v[2][1].pop_back();
				ans.emplace_back(0, x);
				ans.emplace_back(2, 0);
				ans.emplace_back(1, 0);
				have = 2;
			}
			else if (ssize(v[0][1])) {
				auto x = v[0][1].back();
				v[0][1].pop_back();
				ans.emplace_back(0, x);
				ans.emplace_back(2, 0);
				have = 0;
			}
			else {
				ans.pop_back();
				have = 0;
			}
		}
		else if (have == 2) {
			if (ssize(v[1][2])) {
				auto x = v[1][2].back();
				v[1][2].pop_back();
				ans.emplace_back(0, x);
				ans.emplace_back(2, 0);
				ans.emplace_back(1, 0);
				have = 1;
			}
			else if (ssize(v[0][2])) {
				auto x = v[0][2].back();
				v[0][2].pop_back();
				ans.emplace_back(0, x);
				ans.emplace_back(2, 0);
				have = 0;
			}
			else {
				ans.pop_back();
				have = 0;
			}
		}
		else {
			assert(false);
		}
	}
	debug(v);

	cout << ssize(ans) << '\n';
	for (auto [type, x] : ans) {
		if (type == 0) {
			cout << "DRIVE " << x + 1 << '\n';
		}
		else if (type == 1) {
			cout << "PICKUP\n";
		}
		else if (type == 2) {
			cout << "DROPOFF\n";
		}
		else
			assert(false);
	}
}