solution.cpp

#include <bits/stdc++.h>
using namespace std;
long pow_2(int b)
{
    long x = 2;
    long res = 1;
    while (b > 0)
    {
        if (b & 1)
            res = x;
        b >>= 1;
        x = x * x;
    }
    return res;
}
int gcd(long a, long b)
{
    if (b == 0)
        return a;
    return gcd(b, a % b);
}
int main()
{
    cout << gcd(pow_2(20) - 1, pow_2(19)) << endl;
    cout << pow_2(20) - 1 << "/" << pow_2(19) << endl;
}