Random

// import packages
#include <iostream>
#include <string>
#include <cctype>

// import standard c++ library
using namespace std;

int main()
{
    // declare variables
    string input,
           lowerInput = "",
           newString = "";
    int vowels = 0;

    // prompt user for input
    cout << "Please enter a string.\n";
    cin >> input;

    // determine if user input equals "end"
        for (int k = 0; k < input.length() - 1; k++)
        {
            lowerInput += tolower(input.at(k));
            if (lowerInput == "end")
            return 0;
        }

    // find vowels within string
    for (int i = 0; i < input.length() - 1; i++)
    {
        if (lowerInput.at(i) == 'a' || 'e' || 'i' || 'o' || 'u')
        {
            // append underscore after vowel
            newString += input.at(i) + "_";
            vowels++;
        }
    }

    // output amount of vowels and resulting string
    cout << "Vowels: " << vowels << endl
         << "Modified string: " << newString << endl;

    // exit program
    return 0;
}