PAT 1077

 1 #include <vector>
 2 #include <iostream>
 3 #include <string>
 4 #include <algorithm>
 5 #include <limits>
 6 #include <cstdio>
 7 
 8 using namespace std;
 9 
10 int main(){
11     int N;
12     cin >> N;
13     getchar();
14 
15     vector<string> lines;
16     int shortest = 0x7fffffff;
17     for (int i = 0; i < N; i++){
18         string str;
19         getline(cin, str);
20 
21         if (str.size() < shortest)
22             shortest = str.size();
23 
24         lines.push_back(str);
25     }
26 
27     int common_len = 0;
28     for (int i = 0; i < shortest; i++){
29         char ch = lines[0][lines[0].size() - i - 1];
30 
31         int cnt = 1;
32         for (int j = 1; j < lines.size(); j++){
33             string cur_str = lines[j];
34             if (cur_str[cur_str.size() - i - 1] != ch)
35                 break;
36             cnt++;
37         }
38 
39         if (cnt == lines.size())
40             common_len++;
41         else
42             break;
43     }
44 
45     if (common_len == 0)
46         cout << "nai" << endl;
47     else{
48         string res = lines[0].substr(lines[0].size() - common_len, lines[0].size());
49         cout << res << endl;
50     }
51 
52     return 0;
53 }