#include<bits/stdc++.h>
using namespace std;

int n, k;
string s, ss, ans;

string calc(string t){
    if (k==1) return t;
    string res=""; char c=t.back();
    while (t.size()&&t.back()==c){
        res+=t.back(); t.erase(--t.end());
    }
    for (int las=k-1;las--&&res.size()<n;){
        res=res+res; if (res.size()>n) res.resize(n);
    }
    while (res.size()<n){
        res+=t.back(); t.erase(--t.end());
    }
    return res;
}

int main(){
    cin>>n>>k>>s;
    ans="z"; ans[0]+=1;
    ss=s; reverse(ss.begin(),ss.end());
    ss=s+ss;
    for (int i=0;i+n<=ss.length();++i)
        ans=min(ans,calc(ss.substr(i,n)));
    cout<<ans<<endl;
}