Find the maximum possible length of a symmetric fragment which can be obtained after replacing question marks in a given string with $"<"$ or $">".$

Task description

A string made of an even number of characters $("<"$ and$/$or $">")$ is called symmetric if all characters in its first half are $"<"$ and all characters in its second half are $">".$ Examples of symmetric strings are: $""($empty string$),"<>","<<>>","<<<>>>",$ etc.

Write a function:

function solution$($S$)$;

that, given a string S made of N characters $("<",">"$ and$/$or $"?")",$ returns the length of the longest symmetric substring that can be obtained after replacing question marks with $"<"$ or $">"$ characters.

Examples:

$1.$ For S $="<>>",$ after replacing all question marks with $"<",$ the string $"<><<<>>"$ is obtained. Its longest symmetric substring is $"<<>>",$ so the function should return $4.$

$2.$ For S $="??????",$ the optimal option is to replace the first three question marks with $"<"$ and the next three question marks with $">",$ thus obtaining the string $"<<<>>>".$ The function should return $6.$

$3.$ For S $="<\text{'}$ and$/$or $\text{'}?\text{'}.$