#include<iostream>
#include<cstdio>
using namespace std;
const int N=100000+13;
int a[N],n,k,ss;
char s[N];
inline bool check(int x){
	int sum=0;
	for(int i=1,len=0,p=-1;i<=n;++i){
		if(a[i]!=p) p=a[i],len=1;
		else{
			if(len==x) ++sum,p=a[i]^1,len=1;
			else ++len;
		}
	}
	return sum<=k;
}
int main(){
	scanf("%d%d",&n,&k);
	scanf("%s",s+1);
	for(int i=1;i<=n;++i) a[i]=(s[i]=='N'),ss+=(a[i]==(i%2));
	if(ss<=k||(n-ss)<=k){printf("1\n");return 0;}
	int l=2,r=n,mid;
	while(l<r){
		mid=(l+r)>>1;
		if(check(mid)) r=mid;
		else l=mid+1;
	}
	printf("%d\n",l);
	return 0;
}