y=0;p=0;m=9;X={}
L=io.read()
for i=1,L:len()do
c=L:byte(i)
y=y+(c>p and 1 or(c<p and -1)or 0)
m=y<m and y or m
X[y]=X[y]or{};X[y][i]=c 
p=c
end
for i=#X,m,-1 do
C=""
for j=1,L:len()do
C=C..string.char(X[i][j]or 32)
end
print((C:gsub(" +$","")))
end