1210.txt

#include <cstdlib>
#include <iostream>
#include <math.h>

using namespace std;

int main(int argc, char *argv[])
{
     unsigned long long n,i,a,cem=0;
     scanf("%llu%llu",&n,&a);

     if(a==1)
     printf("%llu\n",n*(n+1)/2);
     else
     {
            for(i=1; i<=n; i++)
            cem=cem+i*pow(a,i);
    
            printf("%llu\n",cem);
     }
  
    system("PAUSE");
    return EXIT_SUCCESS;
}