#include <iostream>
using namespace std;
const int mod=19930726;
int n,k;
long long res=1;
char s[1000010];
int main () {
    freopen("rehearse.in","r",stdin);
    freopen("rehearse.out","w",stdout);
    scanf("%d%d",&n,&k);
    for (int i=1;i<=n;i++) cin >> s[i];
    for (int i=n;i>=1;i-=2) {
        for (int l=1;l+i-1<=n;l++) {
            int flag=0;
            for (int j=l;j<(j+i)/2;j++) {
                //cout << j <<' '<< l+i-j <<endl;
                //cout << s[j] <<' '<< s[l+i-j] <<endl;
                if (s[j]!=s[l+i-j]) {
                    flag=1;
                    break;
                }
            }
            if (flag==0) {
                k--;
                res*=i;
                res%=mod;
                if (k==0) {
                    cout << res <<endl;
                    return 0;
                }
            }
        }
    }
    cout << -1 <<endl;
    return 0;
}