[BZOJ1053][HAOI2007]反素数ant

#include <cstdio>
typedef long long ll;
ll n,mx,ans;
ll p[20]={0,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47};

void DFS(ll x,ll last,ll tot,ll val){
if(tot>mx||tot>=mx&&val<=ans){
mx=tot;
ans=val;
}
for(ll i=last;i;i--){
ll t=val;
for(ll j=1;j<=i;j++){
t*=p[x];
if(t>n) break;
}
if(t>n) continue;
DFS(x+1,i,tot*(i+1),t);
}
}

int main(){
scanf("%lld",&n);
DFS(1,31,1,1);
printf("%lld\n",ans);

return 0;
}