### BUGGY CODE ###

n = int(input())
s = str(input())

ans = 0
for xxx in range(1000):
  x = str(xxx).zfill(3)
  ck1,ck2,ck3 = 0,0,0
  start = 0
  for i in range(start,n):
    if(s[i] == x[0]):
      ck1 = 1
      start = i+1
      break
  if(ck1):
    for i in range(start,n):
     if(s[i] == x[1]):
       ck2 = 1
       start = i+1
       break
  if(ck1 and ck2):
    for i in range(start,n):
     if(s[i] == x[2]):
       ans += 1
       break

print(ans)

### FIXED CODE ###

n = int(input())
s = str(input())

#n = 10000
#s = '8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888818888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888388888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888828888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888885888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888898888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888388888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888488888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888788888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888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8'

import re
s = re.sub('[0]{4,}','000',s)
s = re.sub('[1]{4,}','111',s)
s = re.sub('[2]{4,}','222',s)
s = re.sub('[3]{4,}','333',s)
s = re.sub('[4]{4,}','444',s)
s = re.sub('[5]{4,}','555',s)
s = re.sub('[6]{4,}','666',s)
s = re.sub('[7]{4,}','777',s)
s = re.sub('[8]{4,}','888',s)
s = re.sub('[9]{4,}','999',s)

n = len(s)
ans = 0
target = [0] * 10
for i in s:
  target[int(i)] = 1

for xxx in range(1000):
  x = str(xxx).zfill(3)
  if(not (target[int(x[0])] and target[int(x[1])] and target[int(x[2])])):
    continue

  ck1,ck2,ck3 = 0,0,0
  start = 0
  for i in range(start,n):
    if(s[i] == x[0]):
      ck1 = 1
      start = i+1
      break
  if(ck1):
    for i in range(start,n):
     if(s[i] == x[1]):
       ck2 = 1
       start = i+1
       break
  if(ck1 and ck2):
    for i in range(start,n):
     if(s[i] == x[2]):
       ans += 1
       break

print(ans)