package main

import . "fmt"

func main() {
	var n int
	var s string
	Scan(&n,&s)
	var ans int
	x1 := []byte(s)
	for i1, c1 := range x1 {
		x2 := x1[i1+1:]
		for i2, c2 := range x2 {
			if c1 == c2 {
				continue
			}
			x3 := x2[i2+1:]
			for i3, c3 := range x3 {
				if c1 != c3 {
					continue
				}
				x4 := x3[i3+1:]
				for i4, c4 := range x4 {
					if c1 == c4 || c2 == c4 {
						continue
					}
					x5 := x4[i4+1:]
					for _, c5 := range x5 {
						if c1 == c5 || c2 == c5 || c4 == c5 {
							continue
						}
						ans++
					}
				}
			}
		}
	}
	Println(ans)
}