Best way to redirect 301 to https & www

I want to redirect 301:

http://example.com
http://www.example.com

TO

https://www.example.com

I put this code, but it does not work (error 500)

RewriteEngine On
RewriteBase /
RewriteCond %{HTTPS} off           [OR]
RewriteCond %{HTTP_HOST} ^example.com [NC]
RewriteRule ^(.*)$ http://ift.tt/2ifqYp0} [R=301,L, NE]