#include<stdio.h>
#include<math.h>
double emi(double p,double r,int n){
    if(n==0)
    return -1;
    double c=r/(12*100);
    double a=p*c*pow(1+c,n);
    double b=(pow(1+c,n))-1;
    printf("%d",a/b);
    
}
int main(){
    double p,r;
    int n;
    scanf("%lf %lf %d ",&p, &r, &n);
     if(n<0){
        printf("Invalid input");
        return 0;
    }
    double result=emi(p,r,n);
    if(result<0)
    {
        printf("Invalid input");
        return 0;
    }
    printf("%.2lf",result);
    return 0;
}