Interleave Three Equal-Length Strings

Problem

You are given three strings s1, s2, and s3, all of equal length. Your task is to produce a new string by taking the characters column-wise: at each index i, first take s1[i], then s2[i], then s3[i], and concatenate them in that order.

Implement the function:

def interleave(s1: str, s2: str, s3: str) -> str:
    ...

Input Format

• The input consists of three lines, each containing one of the strings.

Output Format

• Print the resulting interleaved string.

Constraints

• 1 <= len(s1) = len(s2) = len(s3) <= 10^5
• Strings may contain letters, digits, or common printable characters.

Example

Input:

abc
def
ghi

Output:

adgbehcfi

Explanation: For index 0, we take 'a', 'd', 'g' → 'adg'; index 1 gives 'b', 'e', 'h' → 'beh'; index 2 gives 'c', 'f', 'i' → 'cfi'. Concatenating these yields 'adgbehcfi'.

s1 = abc
s2 = def
s3 = ghi

adgbehcfi