#include <bits/stdc++.h>
#define l_ength size
const int inf = (1<<30);
const int mod = 1000000007;
using ll = long long;
using namespace std;

int main(){
	int n, k; cin >> n >> k;
	string str; cin >> str;
	char c_min = 'z';
	for( char c : str ) c_min = min( c, c_min );
	if( k < 14 ){
		string tmp = "";
		while( k-- ){
			tmp += str; reverse( str.begin(), str.end() );
			tmp += str;
			if( k > 0 ) reverse( tmp.begin(), tmp.end() );
			vector<string> candy;
			for( int i = 0; i <= n; ++i ){
				candy.push_back( tmp.substr(i, n) );
			}
			sort( candy.begin(), candy.end() );
			str = candy.front();
			if( k > 0 ) reverse( str.begin(), str.end() );
			// cout << str << endl;
			tmp = "";
			if( k == 0 ){
				cout << str << endl;
				return 0;
			}
		}
	}
	else{
		string ans = "";
		while( n-- ){
			ans += c_min; 
		}
		cout << ans << endl;
	}
	return 0;
}