There acting S representing a positive number consisting of N digits. In one moveon choose some digit of S that is not equal to $5$ and replace it with the digit $5.$ What is the maximum number that can be obtained after making exactly K moves?

Write a function:

string solution$($string &S$,$ int K$)$;

that, given a string S and an integer K$,$ returns a string representing the maximum value that can be obtained after making exactly K moves. If making exactly K moves is impossible, return "IMPOSSIBLE".

Examples:

$1.$ Given S$=^\{*\}165232^\{\backslash$circ$\}$ and K$=3$ the function should return $"565552".$ This is the largest number that can be achieved by replacing three digits that are not already $5$s with $5$s$.$

$2.$ Given S $="1839558"$ and K$=4$ the function should return $"5855555".$

$3.$ Given S$=^\{*\}5567855^\{\backslash$circ$\}$ and K$=4$ the function should return "IMPOSSIBLE. It is not possible to make four moves because S contains only three digits that are not $5$s$.$

Write an efficient algorithm for the following assumptions:

N is an integer within the range $[1.\mathrm{.}100,000)$ onenes within the rannen $10000$nt$-$