Poetic word

Dhinwaji is an acclaimed poet and likes to play with words and letters. He has bought some stickers where each sticker has a lower case english letter (a-z). The letters are indexed from 1 - 26 i.e. `a` has index 1, `b` has index 2 and so on. He has $a_i$ stickers with letter $i$ on it. He needs to create a new word having exactly $n$ letters. Being a programmer, Dhinwaji imposed another constrain