n,k=map(int,input().split())
s=input()
j=1
cnt=1
while j<n:
    j*=2
    cnt+=1
if k>=cnt:print(min(s)*n)
else:
    if k==1:
        minstr=s+s[::-1]
    for i in range(k-1):
        s=s+s[::-1]
        minstr=s[:n]
        for j in range(n+1):
            if s[j:j+n]<minstr:
                minstr=s[j:j+n]
        s=minstr[::-1]
    if k>=2:
        minstr=minstr[::-1]+minstr
    ans=minstr[:n]
    for i in range(n+1):
        if ans > minstr[i:i+n]:
            ans=minstr[i:i+n]
    print(ans)