#include <iostream>
#include <string>

int main() {
    std::string str = "Hello, world!";
    char target = 'o';

    for (int i = 0; i < str.length(); i++) {
        if (str[i] == target) {
            std::cout << "Found '" << target << "' at index " << i << std::endl;
        }
    }

    return 0;
}