import java.util.Scanner

//
fun _Do() {
    
    val N = scan.nextInt()
    val S = strings(N)
    val T = strings(N)
 
    var c=0
    for(i in S.indices){
        if(S[i]!=T[i]){
            break
        }
        c++
    }
    
    println(c+1)
    println(S[c])
    println(T[c])
}

var scan = Scanner(System.`in`)
fun main( argv : Array<String> ) {
    _Do()
}

fun strings(N:Int):Array<String> = Array(N,{scan.next()})
fun ints(N:Int):Array<Int> = Array(N,{scan.nextInt()})
fun longs(N:Int):Array<Long> = Array(N,{scan.nextLong()})