let Nstr: String? = readLine()
let N: Int = Int(Nstr!)!
let A: String? = readLine()
let B: String? = readLine()
let C: String? = readLine()

var all = 0
var two = 0
var one = 0

for i in 1 ... N {
    if A![A!.index(A!.startIndex, offsetBy: i - 1)] == B![B!.index(B!.startIndex, offsetBy: i - 1)] && A![A!.index(A!.startIndex, offsetBy: i - 1)] == C![C!.index(C!.startIndex, offsetBy: i - 1)] {
        all += 1
    } else {
        if A![A!.index(A!.startIndex, offsetBy: i - 1)] != B![B!.index(B!.startIndex, offsetBy: i - 1)] && A![A!.index(A!.startIndex, offsetBy: i - 1)] != C![C!.index(C!.startIndex, offsetBy: i - 1)]  && B![B!.index(B!.startIndex, offsetBy: i - 1)] != C![C!.index(C!.startIndex, offsetBy: i - 1)] {
            one += 1
        } else {
            two += 1
        }
    }
}
 print(two + one * 2)
