#include <iostream>
using namespace std;
int main() {
// Citim numărul n
int n;
cin >> n;
// Extragem cifra caracteristică a primei planete
int temp = n;
int prima_cifra = temp % 10;
while (temp >= 10) {
temp /= 10;
prima_cifra = temp % 10;
}
//int count = 0;
//temp = n / 10; // Continuăm cu cifrele rămase (în afară de prima)
//while (temp > 0) {
// int cifra_planetei = temp % 10;
// if (cifra_planetei % prima_cifra == 0) {
// count++;
// }
// temp /= 10;
//}
// Afișăm rezultatul
cout << prima_cifra << endl;
return 0;
}
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