import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val n = nextInt()
    val s = nextLine()
    val s0 = (0 until n).map { s[3 * it] }
    val s1 = (0 until n).map { s[3 * it + 1] }
    val s2 = (0 until n).map { s[3 * it + 2] }
    val c0 = s0.count { it == 'c' }
    val c1 = s1.count { it == 'c' }
    val c2 = s2.count { it == 'c' }
    val o0 = s0.count { it == 'o' }
    val o1 = s1.count { it == 'o' }
    val o2 = s2.count { it == 'o' }
    val n0 = s0.count { it == 'n' }
    val n1 = s1.count { it == 'n' }
    val n2 = s2.count { it == 'n' }
    val x0 = n - c0 - o0 - n0
    val x1 = n - c1 - o1 - n1
    val x2 = n - c2 - o2 - n2
    val con0 = minOf(c0, o1, n2)
    val con1 = minOf(c1, o2, n0)
    val con2 = minOf(c2, o0, n1)
    val con = con0 + con1 + con2
    if (con0 > 0 && con1 > 0 && con2 > 0 && x0 == 0 && x1 == 0 && x2 == 0 && con == n) {
        println(con - 1)
    } else {
        println(con)
    }
}

class UnionFind(n: Int) {
    private val rank = IntArray(n) { 0 }
    private val parent = IntArray(n) { -1 }

    fun find(x: Int): Int {
        if (parent[x] < 0) {
            return x
        }
        parent[x] = find(parent[x])
        return parent[x]
    }

    fun unite(x: Int, y: Int) {
        val x1 = find(x)
        val y1 = find(y)
        if (x1 == y1) {
            return
        }
        if (rank[x1] < rank[y1]) {
            parent[y1] += parent[x1]
            parent[x1] = y1
        } else {
            parent[x1] += parent[y1]
            parent[y1] = x1
            if (rank[x1] == rank[y1]) {
                rank[x1]++
            }
        }
    }

    fun same(x: Int, y: Int): Boolean {
        return find(x) == find(y)
    }

    fun size(x: Int): Int {
        return -parent[find(x)]
    }
}

fun main() {
    Thread(null, {
        val writer = PrintWriter(System.out, false)
        writer.solve()
        writer.flush()
    }, "solve", abs(1L.shl(26)))
        .apply { setUncaughtExceptionHandler { _, e -> e.printStackTrace(); kotlin.system.exitProcess(1) } }
        .apply { start() }.join()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()
fun nextDouble() = next().toDouble()
// endregion