04. Digits, Letters and Other

#include <iostream>

using namespace std;

int main() {
    string str, digits, letters, other;
    cin >> str;

    for (int i = 0; i < str.length(); i++) {
        if (isdigit(str[i])) {
            digits += str[i];
        }
        else if (isalpha(str[i])) {
            letters += str[i];
        }
        else {
            other += str[i];
        }
    }

    cout << digits << endl
        << letters << endl
        << other << endl;
    return 0;
}