Imagemagick is not installing?

rails

#1

for c9 imagemagick is not getting install. its shows as below while installing imagemagick .

Reading package lists… Done
Building dependency tree
Reading state information… Done
Package imagemagick is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package ‘imagemagick’ has no installation candidate


#2

try running sudo apt-get update first