// editor1
#include<stdio.h>
#include<math.h>
 void cemi(double *p, double *annualrate,int *N,double *emi){
 if(*N==0){
     *emi=-1;
     return;
 } 
 double r =(*annualrate)/(12.0*100.0);
 double power =pow(1+r,*N);
 *emi=(*p)*r*power/(power-1);
    }   
 int main(){
     double P,R,emi;
     int N;
     scanf("%lf,%lf,%d",&P,&R,&N);
     calculateEMI(&P,&R,&N,&emi);
     if(emi < 0){
         printf("Invalid input");
         return 0;
     }
 printf("%2f",emi);
 return 0;
     
 }