#include <iostream>
#include <string>
using namespace std;
 
int digitalRoot(int n) {
    while (n > 9) {
        int sum = 0;
        string numString = to_string(n);
        for (char digit : numString) {
            sum += digit - '0';
        }
        n = sum;
    }
    return n;
}
 
int main() {
    int num;
    cout << "Введите натуральное число: ";
    cin >> num;
    int result = digitalRoot(num);
    cout << "Цифровой корень: " << result << endl;
    return 0;
}

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