#include<cstdio>
#include<iostream>
#include<algorithm>
#include<bits/stdc++.h>
using namespace std;
const int n=3000;
int N,D;
char a[n];
int f[n];
int a1,a2;
int main(){
scanf("%d%d",&N,&D);
//memset(f,0x3fffff,sizeof(f));
for(int i=1;i<=N;i++){
scanf(" %c",&a[i]);//在这里一定要注意前面有空格,我当时就错了,搞了半天还是对博客看出来的!!!
f[i]=0x7fffff;
}
f[0]=0;
for(int i=1;i<=N;i++){
for(int j=i;j>=1;j--){
if(a[j]=='H')a1++;
if(a[j]=='J')a2++;
if(a1==0||a2==0||abs(a1-a2)<=D){
f[i]=min(f[i],f[j-1]+1);
}
}
a1=0;a2=0;
}
printf("%d\n",f[N]);
return 0;
}