#include <fstream>
#include <map>
#include <string>
using namespace std;
ifstream f("bilete.in");
ofstream g("bilete.out");
map<char,int,less<char>> x,ul;
int main()
{
 char a[120];
 int i,nr=0,n,j;
 f.get(a,120);
 n=strlen(a);
 for (i=0;i<n;i++)
 {
  if (x[a[i]]==0)
  {
   nr++;
   x[a[i]]=1;
   ul[a[i]]=i;
  }
  else
   if (a[i]!=a[i-1])
   {
    for (j=ul[a[i]]+1;j<i;j++)
     if (a[j]!=a[i]&&x[a[j]])
      x[a[j]]=0;
   }
 }
 g<<nr<<"\n";
 return 0;
}