#include<stdio.h>
#include<math.h>

int main(){
    
    int p,r,n;
    
    scanf("%d %d %d",&p,&r,&n);
    
    int b=1+r;
    int a=pow(b,n);
    
    n1= p*r*a;
    float emi = n1/ a-1;
    
    printf("%.2f",emi);
    
    return 0;
}