#include <stdio.h>
#include <string.h>

char s1[1001], s2[1001];
char res[1001];
int dp[1001][1001];

int max(int a, int b) {
    return a > b ? a : b;
}

int main() {
    scanf("%s", s1);
    scanf("%s", s2);
    int l1 = strlen(s1), l2 = strlen(s2);

    for(int i=1; i<=l1; i++) {
        char c1 = s1[i-1];
        
        for(int j=1; j<=l2; j++) {
            char c2 = s2[j-1];
            
            if(c1 == c2) dp[i][j] = dp[i-1][j-1] + 1;
            else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
        }
    }

    printf("%d\n",dp[l1][l2]);

    if(dp[l1][l2] != 0) {
        int res_len = dp[l1][l2];

        int p1 = l1, p2 = l2;

        while(p1 > 0 && p2 > 0) {
            if(dp[p1][p2] == dp[p1-1][p2]) p1--;
            else if(dp[p1][p2] == dp[p1][p2-1]) p2--;
            else {
                res[--res_len] = s1[p1-1];
                p1--; p2--;
            }
        }

        printf("%s\n", res);
    }

    return 0;
}