_9

/* a
#include <iostream>
using namespace std;

int main()
{

 unsigned long n,E=0,nr,i=1,cif1,cif2;

 cin>>n;

 while (i<=n)
 {
     cif1=i;
     cif2=i+1;
     nr=cif1*10+cif2;
   i++;
     E+=nr;
 }

 cout<<E;

   return 0;
}
//*/
/// e=12+23+34+....+nr(n(n+1))


/* b
#include <iostream>
using namespace std;

int main()
{

 unsigned long n,E=0,nr=0,i=1,nrant=0;

 cin>>n;

   while (i<=n)
   {

       nr=nr*10+i;

       E+=nr;

       if (nr==0)
        nr=1;

        i++;

   }
 cout<<E;

   return 0;
}
//*/
/// e=1+12+123+1234+...nr(1234...n)