UVA 11971 Polygon

#include<bits/stdc++.h>
#include<stdio.h>
#include<iostream>
#include<cmath>
#include<math.h>
#include<queue>
#include<set>
#include<map>
#include<iomanip>
#include<algorithm>
#include<stack>
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
ll gcd(ll a,ll b)
{
    return b==0?a:gcd(b,a%b);
}

ll mypow(int a,int b)
{
    ll res=1;
    while(b--)res*=a;
    return res;
}

//分数类
struct Fraction{
    long long num;
    long long den;
    Fraction(long long num=0,long long den=1){
        if(den<0){
            num=-num;
            den=-den;
        }
        assert(den!=0);
        long long g=gcd(abs(num),den);
        this->num=num/g;
        this->den=den/g;
    }
    Fraction operator+(const Fraction&o)const {
        return Fraction(num*o.den+den*o.num,den*o.den);
    }
    Fraction operator-(const Fraction&o)const{
        return Fraction(num*o.den-den*o.num,den*o.den);
    }
    Fraction operator*(const Fraction &o)const{
        return Fraction(num*o.num,den*o.den);
    }
    Fraction operator/(const Fraction&o)const{
        return Fraction(num*o.den,den*o.num);
    }
    bool operator<(const Fraction &o)const{
        return num*o.den<den*o.num;
    }
    bool operator==(const Fraction&o)const{
        return num*o.den==den*o.num;
    }
};


int id=1;
int main()
{
#ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
#endif // ONLIN
    int t;int n,k;
    cin>>t;
    Fraction f1(1,1);
    while(t--)
    {
        cin>>n>>k;
        Fraction f(k+1,mypow(2,k));
        Fraction ans;
        ans=f1-f;
        cout<<"Case #"<<id++<<": ";
        cout<<ans.num<<"/"<<ans.den<<endl;
    }
}