#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;int OutputBigClient(map<string, pair<string, string>> &r, int n,string &head, vector<string> &output){if (head == "*")    return -1;if (r.find(head) == r.end()){if (n == 0)    output.push_back(head);return 0;}int ans = 2;ans += OutputBigClient(r, n, r[head].first, output);ans += OutputBigClient(r, n, r[head].second, output);if (ans >= n)output.push_back(head);return ans;
}
int main() {int m, n;cin >> m;cin >> n;map<string, pair<string, string>> rec_list;vector<string> output;string x, y, z;for (int i = 0; i < m; i++){cin >> x >> y >> z;rec_list[x] = make_pair(y, z);}x = "A";OutputBigClient(rec_list, n, x, output);if (!output.empty()){cout << output[0];for (int i = 1; i < output.size(); ++i){cout << " " << output[i];}cout << endl;}else{cout << "None" << endl;}//system("Pause");return 0;
}

m, n= [int(i) for i in raw_input().split()]referDict = {}
for _ in range(m):referList = raw_input().strip().split()if referList[0] not in referDict:referDict[referList[0]] = '*'if not referList[1] == '*':referDict[referList[1]] = referList[0]if not referList[2] == '*':referDict[referList[2]] = referList[0]referNum = {i:0 for i in referDict.keys()}for i in referDict:aa= iwhile referDict[aa] in referNum:aa = referDict[aa]referNum[aa] += 1resultList = []
for k,v in referNum.iteritems():if v>=n:resultList.append(k)if len(resultList)==0:print "None"
else:print " ".join(resultList)