#include <iostream>
#include <iomanip>
using namespace std;
int main() {
int number, sumOfDigits = 0, multOfDigits = 1;
cin >> number;
while (number) {
multOfDigits *= number % 10;
sumOfDigits += number % 10;
number /= 10;
}
cout << fixed << setprecision(3) << (double)multOfDigits / sumOfDigits << endl;
return 0;
}
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