#define maxim(a, b) ((a > b) ? a : b)  
 #define FOR(i, a, b) for (i = a; i <= b; ++i)  
 #define NMax 1024  
   
 int M, N, A[NMax], B[NMax], D[NMax][NMax], sir[NMax], bst;  
   
 int main(void)  
 {  
     int i, j;  
       
     freopen("cmlsc.in", "r", stdin);  
     freopen("cmlsc.out", "w", stdout);  
   
     scanf("%d %d", &M, &N);  
     FOR (i, 1, M)  
         scanf("%d", &A[i]);  
     FOR (i, 1, N)  
         scanf("%d", &B[i]);  
   
     FOR (i, 1, M)  
         FOR (j, 1, N)  
             if (A[i] == B[j])  
                 D[i][j] = 1 + D[i-1][j-1];  
             else  
                 D[i][j] = maxim(D[i-1][j], D[i][j-1]);  
   
     for (i = M, j = N; i; )  
         if (A[i] == B[j])  
             sir[++bst] = A[i], --i, --j;  
         else if (D[i-1][j] < D[i][j-1])  
             --j;  
         else  
             --i;  
   
     printf("%d\n", bst);  
     for (i = bst; i; --i)  
         printf("%d ", sir[i]);  
   
     return 0;  
 }