/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author majk
 */

#ifndef MAJK_LIB
#define MAJK_LIB

#include <vector>
#include <stack>
#include <iostream>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <iomanip>
#include <set>
#include <functional>
#include <algorithm>
#include <numeric>
#include <cassert>
#include <cmath>
#include <string>
#include <queue>
#include <array>
#include <bitset>
using namespace std;

#define x first
#define y second
typedef std::pair<int,int> pii; typedef long long ll; typedef unsigned long long ull; typedef unsigned int ui; typedef pair<ui,ui> puu;

template <typename T, typename U> std::istream&operator>>(std::istream&i, pair<T,U>&p) {i >> p.x >> p.y; return i;}
template<typename T>std::istream&operator>>(std::istream&i,vector<T>&t) {for(auto&v:t){i>>v;}return i;}
template <typename T, typename U> std::ostream&operator<<(std::ostream&o, const pair<T,U>&p) {o << p.x << ' ' << p.y; return o;}
template<typename T>std::ostream&operator<<(std::ostream&o,const vector<T>&t) {if(t.empty())o<<'\n';for(size_t i=0;i<t.size();++i){o<<t[i]<<" \n"[i == t.size()-1];}return o;}
template<typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template<typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;
ui logceil(ll x) { return x?8*sizeof(ll)-__builtin_clzll(x):0; }

namespace std { template<typename T,typename U>struct hash<pair<T,U>>{hash<T>t;hash<U>u;size_t operator()(const pair<T,U>&p)const{return t(p.x)^(u(p.y)<<7);}}; }
template<typename T,typename F>T bsh(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){l=m+1;r=m;}else{h=m-1;}}return r;}
template<typename F> double bshd(double l,double h,const F&f,double p=1e-9){ui r=3+(ui)log2((h-l)/p);while(r--){double m=(l+h)/2;if(f(m)){l=m;}else{h=m;}}return (l+h)/2;}
template<typename T,typename F>T bsl(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){h=m-1;r=m;}else{l=m+1;}}return r;}
template<typename F> double bsld(double l,double h,const F&f,double p=1e-9){ui r=3+(ui)log2((h-l)/p);while(r--){double m=(l+h)/2;if(f(m)){h=m;}else{l=m;}}return (l+h)/2;}
template<typename T> T gcd(T a,T b) { if (a<b) swap(a,b); return b?gcd(b,a%b):a; }


template<typename T>class vector2:public vector<vector<T>>{public:vector2(){} vector2(size_t a,size_t b,T t=T()):vector<vector<T>>(a,vector<T>(b,t)){}};
template<typename T>class vector3:public vector<vector2<T>>{public:vector3(){} vector3(size_t a,size_t b,size_t c,T t=T()):vector<vector2<T>>(a,vector2<T>(b,c,t)){}};
template<typename T>class vector4:public vector<vector3<T>>{public:vector4(){} vector4(size_t a,size_t b,size_t c,size_t d,T t=T()):vector<vector3<T>>(a,vector3<T>(b,c,d,t)){}};
template<typename T>class vector5:public vector<vector4<T>>{public:vector5(){} vector5(size_t a,size_t b,size_t c,size_t d,size_t e,T t=T()):vector<vector4<T>>(a,vector4<T>(b,c,d,e,t)){}};


#endif

#include <type_traits>

// ordinary suffix array with optional LCP and LCP RMQ. look elsewhere
template<typename Index, bool PrecomputeLCP = false, bool PrecomputeRMQ = false>
class SuffixArray {
public:
	static_assert(PrecomputeLCP || !PrecomputeRMQ, "Must have RMQ for LCP");

	template<typename T>
	explicit SuffixArray(T t):N(t.size()), S(N), I(N), LCP(PrecomputeLCP ? N : 0) {
		typedef typename std::remove_reference<decltype(t[0])>::type Item;
		vector<pair<Item, Index>> TR(N);
		for (Index i = 0; i < N; ++i) { TR[i] = {t[i], i}; }
		sort(TR.begin(), TR.end());
		vector<Index> R(N);
		Index r = R[TR[0].y] = S[TR[0].y] = 0;
		for (Index i = 1; i < N; ++i) {
			R[TR[i].y] = r += (TR[i - 1].x != TR[i].x);
			S[TR[i].y] = i;
		}
		vector<Index> RA(N), SA(N), C(N);
		for (Index k = 1; k < N; k <<= 1) {
			counting_sort(R, C, SA, k, r+1);
			counting_sort(R, C, SA, 0, r+1);
			RA[S[0]] = r = 0;
			for (Index i = 1; i < N; ++i) {
				RA[S[i]] = r += (R[S[i]] != R[S[i-1]] || S[i]+k >= N || S[i-1]+k >= N ||
								R[S[i]+k] != R[S[i-1]+k]);
			}
			swap(RA, R);
			if (R[S[N-1]] == N-1) break;
		}
		for (Index i = 0; i < N; ++i) { I[S[i]] = i; }
		if (PrecomputeLCP) {
			Index k = 0;
			for (Index i = 0; i < N; ++i) {
				if (I[i] == N - 1) {
					LCP[I[i]] = k = 0;
					continue;
				}
				while (i + k < N && S[I[i] + 1] + k < N && t[i + k] == t[S[I[i] + 1] + k]) { ++k; }
				LCP[I[i]] = k;
				if (k > 0) { --k; }
			}
		}
		if (PrecomputeRMQ) {
			RMQ.push_back(LCP);
			for (int p = 0; (1 << p) < N; ++p) {
				RMQ.push_back(RMQ[p]);
				for (int i = 0; i < N - (1 << p); ++i) { RMQ[p + 1][i] = min(RMQ[p + 1][i], RMQ[p][i + (1 << p)]); }
			}
		}
	}

	Index next(Index i) { return (I[i] == N - 1) ? -1 : S[I[i] + 1]; }

	template<typename=std::enable_if<PrecomputeLCP>>
	Index lcp(Index i) const { return LCP[I[i]]; }

	template<typename=std::enable_if<PrecomputeRMQ>>
	Index lcp(Index i, Index j) const {
		i = I[i];
		j = I[j];
		if (i > j) { swap(i, j); }
		if (i == j - 1)return LCP[i];
		Index p = 0;
		while ((1 << p) < j - i) { ++p; }
		--p;
		return min(RMQ[p][i], RMQ[p][j - (1 << p)]);
	}

	inline void counting_sort(const vector<int> &R, vector<int> &C, vector<int> &SA, int k, int r) {
		Index i;
		fill(C.begin(), C.begin()+r, 0);
		for (i = k; i < N; i++) C[R[i]]++;
		C[0] += k;
		for (Index sum = i = 0; i < r; i++) { C[i] = (sum += C[i], sum - C[i]); }
		if (k) for (i = 0; i < N; i++) { SA[C[S[i]+k<N ? R[S[i]+k] : 0]++] = S[i]; }
		else for (i = 0; i < N; i++) { SA[C[R[S[i]]]++] = S[i]; }
		swap(SA, S);
	}

	Index N;
	vector<Index> S, I, LCP;
	vector<vector<Index>> RMQ;
};
#ifndef MAJK_RANDOM_H
#define MAJK_RANDOM_H

#include <random>
#include <chrono>
auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
std::mt19937 rng(seed);
using random_int = std::uniform_int_distribution<int>;
using random_ll = std::uniform_int_distribution<ll>;
struct TimeLimit {
    TimeLimit(double seconds) : s(seconds-0.2), last(clock()), mx(0) {}
    operator bool() const { clock_t cur = clock(); mx = max(mx, cur-last); last = cur; return clock() < s * CLOCKS_PER_SEC - 1.5 * mx; }
    double s; mutable clock_t last, mx;
};

#endif //MAJK_RANDOM_H


class EReversingAndConcatenating {
public:
    void solve(istream& cin, ostream& cout) {
        int N; cin >> N;
        int K; cin >> K;
        string S; cin >> S;
        string Ans(N, 'z');
        char smallest = *min_element(S.begin(),S.end());
        int longest = 0;
        vector<int> I(N+1);
        for (int i = 0; i <= N; ++i) I[i] = i;
        shuffle(I.begin(),I.end(),rng);
        int suffixes = 0;
        for (int i: I) {
            string A = S;
            string T = A;
            reverse(T.begin(),T.end());
            A += T;
            A = A.substr(i, N);
            if (A[0] != smallest) continue;
            Ans = min(Ans, A);

            if (K >= 2) {
                string T = A;
                reverse(T.begin(),T.end());
                A = T + A;
                int cur = 0, best = 0;
                for (int a: A) {
                    if (a == smallest) {
                        cur++;
                        best = max(best, cur);
                    } else {
                        cur = 0;
                    }
                }
                best = min(best, N);
                if (best < longest || longest == N) continue;
                longest = max(longest, best);

                suffixes++;
                if (suffixes > 1200) continue;

                A += '{';
                SuffixArray<int> SA(A);
                int k = SA.S[0];
                A = A.substr(SA.S[0], N);

                int w = 0;
                while (w < N && A[0] == A[w]) ++w;
                int z = w;
                for (int g = 2; g < K; ++g) {
                    z *= 2;
                    if (z > N) {
                        z = N;
                        break;
                    }
                }


                string Q = string(z, A[0]) + A.substr(w);
                Ans = min(Ans, Q.substr(0, N));
                if (z == N) break;
            }
//            for (int j = 1; j < K; ++j) {
//                string T = A;
//                reverse(T.begin(),T.end());
//                A = T + A;
//                A += '{';
//
//                SuffixArray<int> SA(A);
//                int k = SA.S[0];
//                A = A.substr(SA.S[0], N);
//                if (count(A.begin(),A.end(),A[0]) == N) {
//                    break;
//                }
//            }
//            Ans = min(Ans, A);
        }

        cout << Ans << endl;
    }
};


int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	EReversingAndConcatenating solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
    return 0;
}


Measured memory_bytes: 780