if let in1 = readLine(), let in2 = readLine()
{
    let s1: [Character] = Array(in1)
    let s2: [Character] = Array(in2)
    let (l1, l2) = (s1.count, s2.count)
    var dp: [[Int]] = Array(repeating: Array(repeating: 0, count: l2+1), count: l1+1)
    
    for i in 1...l1 {
        
        let c1 = s1[i-1]
        
        for j in 1...l2 {
            
            let 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])
            }
            
        }
    }
    
    print(dp[l1][l2])
    
    if dp[l1][l2] != 0 {
        var result: String = ""
        var (p1, p2) = (l1, l2)
        
        while !(p1 == 0 || p2 == 0) {
            let (c1, c2) = (s1[p1-1], s2[p2-1])
            
            if c1 == c2 {
                result.append(c1)
                (p1, p2) = (p1-1, p2-1)
            }
            else {
                if dp[p1-1][p2] > dp[p1][p2-1] {
                    p1 -= 1
                }
                else {
                    p2 -= 1
                }
            }
        }
        
        print(String(Array(result).reversed()))
    }
}