/*
读懂题意，bfs即可AC。
关键考虑好，进入队列的是谁。
注意：
在实现的时候，调用std::string::operator+()和string.substr()很多次，会直接导致TLE。。
相同思路，换种实现（考虑使用string.replace()和string.find()），即可AC。
*/
1 #include <iostream>
2 #include <cstdlib>
3 #include <cstdio>
4 #include <cstddef>
5 #include <iterator>
6 #include <algorithm>
7 #include <string>
8 #include <locale>
9 #include <cmath>
10 #include <vector>
11 #include <cstring>
12 #include <map>
13 #include <utility>
14 #include <queue>
15 #include <stack>
16 #include <set>
17 using namespace std;
18 const int INF = -0x3f3f3f3f;
19 const int MaxN = 55;
20 const int modPrime = 3046721;
21
22 struct Node
23 {
24 string str;
25 int stepCnt;
26 };
27
28 Node startOff;
29 string A, B;
30 vector<pair<string, string> > vecStr;
31 set<string> setStr;
32
33
34 void Solve()
35 {
36 queue<Node> queNode;
37 queNode.push(startOff);
38 while (!queNode.empty())
39 {
40 Node node = queNode.front();
41 queNode.pop();
42 string str = node.str;
43 int stepCnt = node.stepCnt;
44 if (node.str == B)
45 {
46 cout << stepCnt << endl;
47 return;
48 }
49 if (stepCnt == 10)
50 {
51 continue;
52 }
53
54 setStr.insert(str);
55 for (int i = 0; i < vecStr.size(); ++i)
56 {
57 for (int j = 0; j < str.size(); ++j)
58 {
59 int pos = str.find(vecStr[i].first, j);
60 if (pos != string::npos)
61 {
62 node.str = str;
63 node.str.replace(pos, vecStr[i].first.size(), vecStr[i].second);
64 if (setStr.find(node.str) == setStr.end())
65 {
66 node.stepCnt = stepCnt + 1;
67 queNode.push(node);
68 setStr.insert(node.str);
69 }
70 }
71 }
72 }
73 }
74 cout << "NO ANSWER!" << endl;
75 }
76
77
78 int main()
79 {
80 #ifdef HOME
81 freopen("in", "r", stdin);
82 //freopen("out", "w", stdout);
83 #endif
84
85 cin >> A >> B;
86 startOff.str = A;
87 startOff.stepCnt = 0;
88 string str1, str2;
89 while (cin >> str1 >> str2)
90 {
91 vecStr.push_back(make_pair(str1, str2));
92 }
93 Solve();
94
95
96 #ifdef HOME
97 cerr << "Time elapsed: " << clock() / CLOCKS_PER_SEC << " ms" << endl;
98 _CrtDumpMemoryLeaks();
99 #endif
100 return 0;
101 }
