import sequtils,strutils,math

var N = stdin.readline

var
    ans = N.parseInt
for a in 0..N.high:
    for b in (a + 1)..N.high:
        (N[a],N[b]) = (N[b],N[a])
        ans = max(ans,N.parseInt)
        (N[a],N[b]) = (N[b],N[a])
echo ans