import java.util.*;

public class PotionBrewer {
    private static final Map<String, List<List<String>>> recipes = new HashMap<>();
    private static final Map<String, Integer> memoization = new HashMap<>();
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int numRecipes = scanner.nextInt();
        scanner.nextLine();
        for (int i = 0; i < numRecipes; i++) {
            String[] recipeParts = scanner.nextLine().split("=");
            String potion = recipeParts[0].trim();
            String[] ingredients = recipeParts[1].split("\\+");
            recipes.computeIfAbsent(potion, k -> new ArrayList<>()).add(Arrays.asList(ingredients));
        }
        String targetPotion = scanner.nextLine();
        scanner.close();
        int result = calculateMinimumOrbs(targetPotion);
        System.out.println(result);
    }
    private static int calculateMinimumOrbs(String potion) {
        if(!recipes.containsKey(potion)){
            return 0;
        }
        if(memoization.containsKey(potion)){
            return memoization.get(potion);
        }
        int minOrbs = Integer.MAX_VALUE;
        for (List<String> recipe : recipes.get(potion)){
            int orbsRequired = recipe.size() - 1;
            for(String ingredient : recipe){
                orbsRequired += calculateMinimumOrbs(ingredient);
            }
            minOrbs = Math.min(minOrbs, orbsRequired);
        }
        memoization.put(potion, minOrbs);
        return minOrbs;
    }
}