1 #include<iostream>
2 #include<fstream>
3 #include<cstring>
4
5 using namespace std;
6 #define MAXN 28
7
8 bool adj[MAXN][MAXN];
9 int indegree[MAXN];
10 char str[MAXN];
11 int n, m;
12
13
14
15
16 int topo_sort()
17 {
18 int i,j,k;
19 int flag = true;
20 memset(indegree,0,sizeof(indegree));
21 memset(str,'\0',sizeof(str));
22 for(i=1; i<=n; i++)
23 {
24 for(j=1; j<=n; j++)
25 if(adj[i][j])
26 indegree[j]++;
27 }
28 for(i=1; i<=n; i++)
29 {
30 k = 0;
31 for(j=1; j<=n; j++)
32 {
33 if(indegree[j]==0)
34 {
35 if(k==0) k = j;
36 else flag = false;
37 }
38 }
39 if(k==0) return 0;
40 indegree[k] = -1;
41 str[i-1] = k+'A'-1;
42 for(j=1; j<=n; j++)
43 {
44 if(adj[k][j])
45 indegree[j]--;
46 }
47 }
48
49 if(flag) return 1;
50 else return 2;
51 }
52
53 int main()
54 {
55
56 int i, a, b, result;
57 char s[4];
58 while (scanf("%d %d", &n, &m),m+n)
59 {
60 memset(adj,false,sizeof(adj));
61 bool h=false;
62 for(i=1; i<=m; i++)
63 {
64 scanf("%s", s);
65 a = s[0]-'A'+1;
66 b = s[2]-'A'+1;
67 adj[a][b] = true;
68 if(h) continue;
69 result = topo_sort();
70 if(result == 1)
71 {
72 printf("Sorted sequence determined after %d relations: %s.\n",i,str);
73 h = true;
74 }
75 if(result == 0)
76 {
77 printf("Inconsistency found after %d relations.\n",i);
78 h = true;
79 }
80 }
81 if(!h)
82 printf("Sorted sequence cannot be determined.\n");
83 }
84
85 return 0;
86 }
