#input of int(split by space)
def get_i()
  return gets.chomp.split(" ").map(&:to_i)
end
#input of float(split by space)
def get_f()
  return gets.chomp.split(" ").map(&:to_f)
end
#input of string(split by space)
def get()
  return gets.chomp.split(" ")
end
#input of string(split per one character)
def get_nsp()
  return gets.chomp.split("")
end
#yes or no decision
def yn_judge(bool,y="Yes",n="No")
  return bool ? y : n 
end
#create of array
def array(size1,init=nil,size2=-1)
  if size2==-1
    return Array.new(size1){init}
  else
    return Array.new(size2){Array.new(size1){init}}
  end
end

def max(a,b)
    return a>b ? a : b
end

def min(a,b)
    return a>b ? b : a
end

INF=Float::INFINITY

N=gets.to_i
S=get_nsp
$ans={}
def dfs(i,k,s)
  #puts "#{k} #{i} #{s}"
  w=array(10,0)
  cnt=0
  i.upto(N-3+k-1) do|j|
      if w[S[j].to_i].zero?
        if k==3
            $ans[s+S[j]]=1
        else
            dfs(j+1,k+1,s+S[j])
        end
        w[S[j].to_i]=1
        cnt+=1
      end
      break if cnt==10
  end
end
dfs(0,1,"")
#p $ans
puts $ans.size