element-gram
% elgram <source> <indices>
# if called with no args, then prompt asks you
% elgram
% elgram 5325733 3212
# => 2353
% elgram somephrase 4321
# => emos
# You'd like to use over 10 characters source, give comma splitted indices.
% elgram super-long-phrase 12,5,4,4
# => pree
% go build -o elgram main.go