Vanya got an important task — he should enumerate books in the library and label each book with its number. Each of the *n* books should be assigned with a number from 1 to *n*. Naturally, distinct books should be assigned distinct numbers.

Vanya wants to know how many digits he will have to write down as he labels the books.
The first line contains integer *n* (1 ≤ *n* ≤ 10<sup class="upper-index">9</sup>) — the number of books in the library.
#include <iostream>

using namespace std;
long long a[12]={0,9,99,999,9999,99999,999999,9999999,99999999,999999999,9999999999};
int main()
{
    long long m;
    while(cin>>m)
    {
        long long  k=1,sum=0;注意是long long 
        if(m<10)
        {
            cout<<m<<endl;
            continue;
        }
        else
        {
            for(int i=1; i<=10; i++)
            {
                k*=10;
                if(m<k)
                {
                    sum+=(m-k/10+1)*i;
                    break;
                }
                else
                    sum+=(a[i]-a[i-1])*i;
            }
            cout<<sum<<endl;
        }
    }
    return 0;
}
					  	 	 		 	    			 	 	 	 		