#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define mp make_pair
#define pii pair<int,int>
inline ll read()
{
ll x=0;
bool pos=1;
char ch=getchar();
for(;!isdigit(ch);ch=getchar())
if(ch=='-')
pos=0;
for(;isdigit(ch);ch=getchar())
x=x*10+ch-'0';
return pos?x:-x;
}
ll n,k;
struct node{
ll a,b,c,d;
node(ll a,ll b,ll c,ll d):a(a),b(b),c(c),d(d) {}
bool operator < (const node &rhs) const
{
return a<rhs.a;
}
};
bool isp(ll x)
{
for(ll i=2;i*i<=x;++i)
if(x%i==0)
return false;
return true;
}
priority_queue<node> hp;
ll pr[130],cnt=0;
int main()
{
n=read(),k=read();
for(ll i=2;i<=128;++i)
{
if(isp(i))
{
pr[++cnt]=i;
ll a=1;
for(ll j=1;a<=n/i;++j)
{
a*=i;
hp.push(node(a,i,0,0));
if(cnt>1 && j>1)
hp.push(node(a/i*pr[cnt-1],i,j-1,cnt-1));
}
}
}
while(--k)
{
node cur=hp.top();
hp.pop();
ll a=cur.a,b=cur.b,c=cur.c,d=cur.d;
if(d>1)
hp.push(node(a/pr[d]*pr[d-1],b,c,d-1));
if(c>1)
hp.push(node(a/b*pr[d],b,c-1,d));
}
cout<<hp.top().a<<endl;
return 0;
}
原文:https://www.cnblogs.com/jklover/p/10435886.html