线性筛+sort
1 #define mm(a) memset(a,0,sizeof(a)); 2 #define max(x,y) (x)>(y)?(x):(y) 3 #define min(x,y) (x)<(y)?(x):(y) 4 #define Fopen freopen("1.in","r",stdin); freopen("m.out","w",stdout); 5 #define rep(i,a,b) for(int i=(a);i<=(b);i++) 6 #define per(i,b,a) for(int i=(b);i>=(a);i--) 7 #include<bits/stdc++.h> 8 typedef long long ll; 9 #define PII pair<ll,ll> 10 using namespace std; 11 const int INF=0x3f3f3f3f; 12 const int MAXN=(int)2e6 + 5; 13 14 struct node 15 { 16 int x; 17 int id; 18 int val; 19 }a[MAXN]; 20 bool vis[MAXN]; 21 int prime[MAXN]; 22 23 int t[MAXN],e[MAXN],n,k; 24 //geshu fuzhu 25 void Init() { 26 int cnt=0; 27 t[1]=1; 28 for(int i=2; i<=MAXN; ++i) { 29 if(!vis[i]) { 30 prime[++cnt]=i; 31 t[i]=2; 32 e[i]=1; 33 } 34 for(int j=1; j<=cnt; ++j) { 35 if(i*prime[j]>MAXN) break; 36 vis[i*prime[j]]=true; 37 if(i%prime[j]==0) { 38 t[i*prime[j]]=t[i]/(e[i]+1)*(e[i]+2); 39 e[i*prime[j]]=e[i]+1; 40 break; 41 } else { 42 t[i*prime[j]]=t[i]*2; 43 e[i*prime[j]]=1; 44 } 45 } 46 } 47 } 48 49 50 int main() { 51 Init(); 52 while(~scanf("%d%d",&k,&n)) { 53 for(int i=1;i<=n;i++)scanf("%d",&a[i].x),a[i].id=i,a[i].val=t[a[i].x]; 54 sort(a+1,a+1+n,[](node a,node b){ 55 if(a.val!=b.val)return a.val<b.val; 56 return a.x<b.x; 57 }); 58 printf("%d\n",a[k].x); 59 } 60 return 0; 61 }