#include<stdio.h>
#include<math.h>
int main(){
    int  P,R,N,result;
    float  emi;
    scanf("%d %d %d",&P,&R,&N);
    if(N==0){
        printf("Invalid input");
        return 0;
    }
    int b=1+R;
    result= pow(b,N);
    emi = P*R*result/(result-1).2f;
    printf("%.2f",emi);
}