import java.util.*;
class abc
{
 public static void main(String ar[])
 {
  Scanner s=new Scanner(System.in);
  int n=s.nextInt();
  int d[]=new int[4];
  int s1=0;
  String y=s.next();
  char c;
  for(int i=0;i<n;i++)
  {
  c=y.charAt(i);
   if(d[0]==1&&d[1]==1&&d[2]==1&&d[3]==1)
   break;
   if(Character.isDigit(c))
   d[0]=1;
   else if(Character.isLowerCase(c))
   d[1]=1;
   else if(Character.isUpperCase(c))
   d[2]=1;
   else
   d[3]=1;
  }
 s1=4-(d[0]+d[1]+d[2]+d[3]);
  if(n+s1-6>0)
System.out.println(s1);
else
System.out.println(6-n);
  
/*System.out.println(d[0]);
System.out.println(d[1]);
System.out.println(d[2]);
System.out.println(d[3]);
System.out.println(s1);
*/}
}