Trailing Zeroes (III) 假设n!后面有x个0.现在要求的是，给定x，要求最小的n； 判断一个n!后面有多少个0，通过n/5+n/25+n/125+...

/**
题目：Trailing Zeroes (III) 
链接：https://vjudge.net/contest/154246#problem/N
题意：假设n!后面有x个0.现在要求的是，给定x，要求最小的n；
思路：判断一个n!后面有多少个0，通过n/5+n/25+n/125+...
*/

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long ll;
const int maxn = 5*1e8+1;
int num(int m)
{
    int cnt = 0;
    while(m>0){
        cnt += m/5;
        m /= 5;
    }
    return cnt;
}
int main()
{
    int T, cas=1, q;
    cin>>T;
    while(T--)
    {
        scanf("%d",&q);
        int lo = 5, hi = maxn;
        int m;
        int mis = maxn;
        while(lo<=hi){
            m = (lo+hi)/2;
            int t = num(m);
            if(t>=q){
                if(t==q) mis = min(mis,m);
                hi = m-1;
            }else
            {
                lo = m+1;
            }
        }
        if(mis==maxn)
            printf("Case %d: impossible
",cas++);
        else
            printf("Case %d: %d
",cas++,mis);

    }
    return 0;
}