UVA 12068 Harmonic Mean (UVALive 3288, Regionals 2005 >> Asia - Dhaka)

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / uva / uvalive), 3235 (lightoj)
///     mail: raihanruhin@ (yahoo / gmail / facebook)
///     blog: ruhinraihan.blogspot.com

#include<bits/stdc++.h>
using namespace std;

#define SET(a) memset(a,-1,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))
#define PI acos(-1.0)

#define MOD 1000000007
#define MX 100010

long long calcLcm(long long a, long long b)
{
    return a*b/__gcd(a, b);
}

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int tc, kk=1, n, m, x, y, a, b, c, arr[12];
    string s;
    cin>>tc;
    while(tc--)
    {
        cin>>n;
        cin>>arr[0];
        long long lcm = arr[0];
        for(int i=1;i<n;i++)
        {
            cin>>arr[i];
            lcm = calcLcm(lcm, arr[i]);
        }
        long long denominator = 0;
        for(int i=0;i<n;i++)
            denominator+=(lcm/arr[i]);
        long long numerator = lcm * n;
        long long gcd = __gcd(numerator, denominator);
        cout<< "Case "<<kk++<<": "<< numerator/gcd<<"/"<<denominator/gcd<<"\n";
    }
return 0;
}