var input = require("fs").readFileSync("input.txt").toString().split("\n").filter(a=>a);
var moves = input.map(line=>(line.split(" "))).map(a=>([a[1], a[7]]));

var statesObj = {};
for(var state of moves.map(a=>(a[0])).concat(moves.map(a=>(a[1])))){
	statesObj[state] = 0;
}
var states = Object.keys(statesObj);
var visited = [];

var workers = [
	[0, ""],
	[0, ""],
	[0, ""],
	[0, ""],
	[0, ""],
]

var i = -1;

while(visited.length < states.length){
	for(var worker of workers){
		if(worker[0] == 0){
			if(worker[1]){
				visited.push(worker[1]);
			}
		}
	}
	var possibleMoves = states.filter(s=>(moves.filter(m=>(m[1]==s)).map(m=>(m[0])).filter(ms=>(visited.indexOf(ms) == -1)).length == 0)).filter(s=>(visited.indexOf(s) == -1)).filter(s=>(workers.map(w=>(w[1])).indexOf(s) == -1)).sort();
	for(var worker of workers){
		if(worker[0] == 0){
			worker[1] = possibleMoves.shift();
			if(worker[1]){
				worker[0] = worker[1].charCodeAt(0) - "A".charCodeAt(0);
				worker[0] += 60;
			}
		}
		else{
			worker[0]--;
		}
	}
	i++;
}
console.log(i);