根据反素数的性质，dfs就好了 反素数讲解：http://blog.csdn.net/ACdreamers/article/details/25049767
#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ULL;
const ULL INF = ~
0ULL;
int p[
16] = {
2,
3,
5,
7,
11,
13,
17,
19,
23,
29,
31,
37,
41,
43,
47,
53};
int n;
ULL ans;
void dfs(
int dept, ULL tmp,
int num)
{
if(num > n)
return;
if(num == n && tmp < ans) ans = tmp;
for(
int i =
1; i <=
63; ++i)
{
if(ans/p[dept] < tmp)
break;
dfs(dept+
1,tmp*=p[dept],num*(i+
1));
}
}
int main()
{
while(
cin >> n)
{
ans = INF;
dfs(
0,
1,
1);
cout << ans << endl;
}
return 0;
}
