How can we divide a number which is not a prime number into the multiply of prime number? Here is a conclusion:

If one number is not a prime number, and can be divided into two or more numbers, than the numbers will be smaller than its sqrt.

For example, input some numbers, you have to print a line in the output for each entry with the divide numbers. The program is:

#include <iostream>

using namespace std;

int main() {
    int N;
    while (cin >> N) {
        for (int i = 2; i * i <= N; i++) {
            if (N % i == 0) {
                N /= i;
                cout << i << "*";
                i = 1;
            }   
        }                   //The key is any number can be divide by 1, and 2 when it's a even 
        				  //number, and 3 when it's a odd number but not a prime number.
        cout << N << endl;
    }   

    return 0;
}