package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func main() {
	sc.Buffer(make([]byte, 1000), 5000000)
	sc.Split(bufio.ScanWords)
	n := nextInt()
	s := nextString()
	a := make([][]int, 3)
	for i := range a {
		a[i] = make([]int, 3)
	}
	for i := range s {
		if s[i] == 'c' {
			a[0][i%3]++
		}
		if s[i] == 'o' {
			a[1][i%3]++
		}
		if s[i] == 'n' {
			a[2][i%3]++
		}
	}
	ans := 0
	for i := range a {
		tmp := a[0][i]
		if a[1][(i+1)%3] < tmp {
			tmp = a[1][(i+1)%3]
		}
		if a[2][(i+2)%3] < tmp {
			tmp = a[2][(i+2)%3]
		}
		ans += tmp
		if ans == n {
			fmt.Println(n)
			return
		}
	}
	if ans == n {
		ans--
	}
	fmt.Println(ans)
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func nextString() string {
	sc.Scan()
	return sc.Text()
}