source_code: import java.util.*;
  
  
  public class Main{
      
      public static void main(String[] args){
          Scanner in = new Scanner(System.in);
          int[] a=new int[1010];
          while(in.hasNext()){
              int n=in.nextInt();
              String s=in.next();
              int sum=0;
              for(int i=0;i<n;++i){
                  if(s.charAt(i)=='H'){
                      a[i]=1;
                      ++sum;
                  }
                  else a[i]=0;
              }
              int min=10010;
              for(int i=0;i<n-sum;++i){
                  int count=0;
                  for(int j=i+sum;j<n;++j){
                      if(a[j]==1)++count;
                  }
                  for(int j=0;j<i;++j){
                      if(a[j]==1)++count;
                  }
                  if(count<min)min=count;
              }
              sum=n-sum;
              for(int i=0;i<n-sum;++i){
                  int count=0;
                  for(int j=i+sum;j<n;++j){
                      if(a[j]==0)++count;
                  }
                  for(int j=0;j<i;++j){
                      if(a[j]==0)++count;
                  }
                  if(count<min)min=count;
              }
              System.out.println(min);
          }
      }
  }
  