CodeFroces--Joseph’s Problem

#include<bits/stdc++.h>
using namespace std;
#define maxn
#define LL long long
int main(){
 // freopen("joseph.in","r",stdin);
 // freopen("joseph.out","w",stdout);
  LL n,k;
  cin>>n>>k;
  LL ans=0;
  if(n>=k){
     ans+=k*(n-k);
     for(LL l=1,r=0;l<=k&&r<=k;l=r+1){
        r=k/(k/l);
        LL len=r-l+1;
        ans+=len*k-(l+r)*len/2*(k/l);
     }
     cout<<ans<<endl;
  }else{
     ans=0;
     for(LL l=1,r=0;l<=k;l=r+1){
        r=k/(k/l);
        if(r>n) r=n;
        LL len=r-l+1;
        ans+=len*k-(l+r)*len/2*(k/l);
        if(r==n) break;
     }
     cout<<ans<<endl;
  }
}