/* Author: Dhruv Rastogi */
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define all(sdk) sdk.begin(),sdk.end()
#define mll map<int, int>
#define pb push_back
#define rep(i,a,b) for(int i=a;i<b;++i)
#define repd(i,a,b) for(int i=a;i>=b;--i)
#define mp make_pair
#define hell 1000000007
#define endl '\n'
#define vvll vector<vector<int> >
#define vll vector<int>
#define mint map<int,int> 
#define sz(x) (int)x.size()
#define sll set<int>
#define pll pair<int,int>
#define F first
#define S second
const long double PI = acos(-1.0);

void solve(){  
	int n,k;
	cin>>n>>k;
	string s;
	cin>>s;
	string t=s;
	reverse(all(t));
	s+=t;
	string mn=s.substr(0,n);
	rep(i,0,n+1){
		mn=min(mn,s.substr(i,n));
	}  
	--k;
	int rl=0;
	rep(i,0,n){
		if(mn[i]!=mn[0])
			break;
		else ++rl;
	}
	rep(i,0,min(k,15)){

		string app(rl,mn[0]);
		mn=app+mn;
		mn=mn.substr(0,n);
		rl*=2;
		rl=min(n,rl);
	}
	cout<<mn<<endl;
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t=1;
    // cin>>t;
    while(t--){
        solve();
    }
    return 0;
}