Count Vowels with a Loop

Summary

Count how many vowels appear in a given string (case-insensitive).

Problem statement

Given an input string, return the number of vowel characters it contains. Vowels are the letters a, e, i, o, u. The function should be case-insensitive — both uppercase and lowercase vowels count. Non-letter characters do not affect the count. This task practices iterating over characters, conditional checks, and simple accumulation.

Task

Write a function that iterates through a string and returns the number of vowels (a, e, i, o, u).

Examples

Input format

A single string argument s passed to the function count_vowels(s).

Output format

An integer representing the count of vowels in the string.

Constraints

The input string length will be between 0 and 10,000 characters. Only English letters are considered; treat other characters as non-vowels. Time complexity should be O(n) where n is the string length.

Samples