#include<iostream>
#include<algorithm>
#define ll long long
using namespace std;
int main(){
	freopen("rehearse.in","r",stdin);
	freopen("rehearse.out","w",stdout);
	
	int n,k;string s;cin>>n>>k>>s;
	ll ans=1;
	string s1=s,s2=s;reverse(s2.begin(),s2.end());
	for(ll len=n;len>=1;len--){
		if(len%2==0) continue;
		for(int i=0;i<=s.length()-len;i++){
			if(s1.substr(i,len)==s2.substr(n-i-len,len)) k--,ans=(ans*len)%19930726;
			if(!k){
				cout<<ans;
				return 0;
			}
		}
	}
	cout<<-1;
	
	return 0;
}