#include <stdio.h>
//d不能是整型 !!
/*s<250 无折扣 s<1
250<=s<500 0.02 1
500<=s<1000 0.05 2 3
1000<=s<2000 0.08 4 5 6 7
2000<=s<3000 0.10 8 9 10 11
3000<=s 0.15 12 13 14
*/
int main()
{
//每千米货物基本运费p 距离s 货物重w 折扣d f总运费 f=p*w*s*(1-d)
double p,w,d,f,s;
int c;
scanf("%lf,%lf,%lf",&p,&w,&s);
if (s>=3000)
c = 12;
else
{
c = s/250;
switch(c)
{
case 0:d = 0;break;
case 1:d = 2;break;
case 2:
case 3:d = 5;break;
case 4:
case 5:
case 6:
case 7:d = 8;break;
case 8:
case 9:
case 10:
case 11:d=10;break;
case 12:d=15;break;
default:break;
}
}
f = p*s*(1-d/100)*w;
printf("%f",f);
return 0;
}