1 #include <stdio.h>
 2 #include <string.h>
 3 
 4 char s1[100010],s2[100010],s3[200010],s4[200010];
 5 int next_[100010];
 6 void getnext(char s[])
 7 {
 8     int i = 0, j = -1;
 9     int len = strlen(s);
10     next_[0] = -1;
11     while(i < len)
12     {
13         if (j == -1 || s[i] == s[j])
14             next_[++ i] = ++ j;
15         else
16             j = next_[j];
17     }
18 }
19 int kmp(char s1[],char s2[])
20 {
21     getnext(s2);
22     int i = 0, j = 0;
23     int len = strlen(s1),len1 = strlen(s2);
24     while (i < len && j< len1)
25     {
26         if (j == -1 || s1[i] == s2[j]){
27             i ++; j++;
28         }
29         else
30             j = next_[j];
31     }
32     if (i == len)
33         return j;
34     return 0;
35 }
36 int main ()
37 {
38     while (~scanf("%s%s",s1,s2))
39     {
40         int l1 = kmp(s1,s2);  // 先求出两种情况重合部分的长短 
41         int l2 = kmp(s2,s1);
42 
43         if (l1 == l2)   // 如果长度相同，判断两个字符串的字典序 
44         {
45             if (strcmp(s1,s2)<0)
46                 printf("%s%s\n",s1,s2+l2);
47             else
48                 printf("%s%s\n",s2,s1+l2);
49         }
50         else if(l1 < l2)
51             printf("%s%s\n",s2,s1+l2);
52         else
53             printf("%s%s\n",s1,s2+l1);
54     }
55     return 0;
56 }