Finding LCM LightOJ - 1215 （水题）

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#define rap(a, n) for(int i=1; i<=n; i++)
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 10010, INF = 0x7fffffff;
LL gcd(LL a, LL b)
{
    return b==0?a:gcd(b, a%b);
}

int main()
{
    int T, kase = 0;
    cin>> T;
    while(T--)
    {
        LL a, b, L;
        cin>> a >> b >> L;
        printf("Case %d: ", ++kase);
        LL c = a * b / gcd(a, b);
        if(L % c)
        {
            cout<< "impossible" <<endl;
            continue;
        }
        LL d = L / c;
        while(gcd(c, d) != 1)
        {
            LL m = gcd(c, d);
            c /= m;
            d *= m;
        }
        cout<< d <<endl;
    }

    return 0;
}