1112 水题

http://sdnuacm.sinaapp.com/problem.php?id=1112


#include<iostream>

usingnamespace std;

intmain()

{

   longlong a,b,c,i;

   longlong sum=0;

 cin>>a>>b>>c;

       for(i=1;i<=a;i++)

          { sum+=b;

            b=b*c;

        }

   cout<<sum<<endl;

   return0;

}