MOD=10**9+7
cnt=0; sum=0; prev=nil; can=true; h=Hash.new(0)
def gs() gets.chomp end
def gi() gets.to_i end
def gsmi() gets.chomp.split.map(&:to_i) end

def desc(ar) ar.sort{|x,y|y<=>x} end##
def min(a,b) a<=b ? a : b end
def max(a,b) a>=b ? a : b end
def sum(ar) ar.inject(:+) end

def C(a,b) b==0||a==b ? 1 : (b=a-b if a/2<b;(a-b+1..a).inject(:*)/(1..b).inject(:*)) end

def puts_yesno(can) puts(can ? 'Yes' : 'No') end
def putsend(s) puts s; exit end
def debug(k,v) puts "#{k}:#{v}" end
########### ( ˘ω˘ )ｽﾔｧ… ###########
n=gi
s=gs
cnt=0
0.upto(9) do |i|
  ii=s.index(i.to_s)
  next if ii.nil? || ii==s.length-1
  0.upto(9) do |j|
    ji=s.index(j.to_s,ii+1)
    next if ji.nil? || ji==s.length-1
    0.upto(9) do |k|
      ki=s.index(k.to_s,ji+1)
      cnt+=1 unless ki.nil?
    end
  end
end

puts cnt