1 var n,k,i,l,r,m:longint; 2     ans:qword; 3 function ceil(x:real):longint; 4  begin 5  if trunc(x)<x then exit(trunc(x)+1) else exit(trunc(x)); 6  end; 7 procedure main; 8  begin 9    readln(n,k);10    ans:=0;11    if n>k then12     begin13      inc(ans,(n-k)*k);14      n:=k;15     end;16    m:=ceil(sqrt(k));17    for i:=1 to m do inc(ans,k mod i);18    for i:=1 to m do19     begin20       l:=(k div (i+1))+1;21       r:=(k div i);22       if l<=m then l:=m+1;23       if r>n then r:=n;24       if r<l then continue;25       inc(ans,(((k<<1)-i*(l+r))*(r-l+1)>>1));26     end;27    writeln(ans);28  end;29 begin30   main;31 end.    

 1 #include <iostream> 2 #include <cmath> 3 using namespace std; 4  5 long long ans,n,k; 6 int main() { 7   ios::sync_with_stdio(false); 8   cin>>n>>k; 9   if (n>k) {10     ans+=k*(n-k);11     n=k;12   }13   long long sqrtk=ceil(sqrt(k));14   for (long long i=1;i<=sqrtk;++i) ans+=k%i;15   for (long long a=1;a<=sqrtk;++a) {16     long long L=floor(k/(a+1))+1;17     long long R=floor(k/a);18     if (L<=sqrtk) L=sqrtk+1;19     if (R>n) R=n;20     if (R<L) continue;21     ans+=((k<<1)-a*L-a*R)*(R-L+1)>>1;22   }23   cout<<ans;24 }

 1 #include <cmath> 2 #include <cstdio> 3 #include <algorithm> 4  5 long long n, k, ans; 6 int main() 7 { 8   scanf("%lld%lld", &n, &k); 9   if (n > k)10   {11     ans += (n-k)*k;12     n = k;13   }14   ans += n * k;15   for (long long i = 1, last; i <= n; i = last+1)16   {17     last = std::min(n, k/(k/i));18     ans -= (k/i) * (i+last) * (last-i+1) / 2;19   }20   printf("%lld", ans);21 }