#include<stdio.h>
int sum,one,month;
double fun(double x)
{
	x/=100; 
	double now_money=sum;
	for(int i=1;i<=month;i++)
		now_money=now_money*(1+x)-one;
	return now_money;
}
int main(void)
{
	scanf("%d%d%d",&sum,&one,&month);
	double begin=0.1,end=100000;
	while(begin<=end-0.0001)
	{
		if(fun((begin+end)/2)>0)	end=(begin+end)/2;
		else if(fun((begin+end)/2)<0)	begin=(begin+end)/2;
		else	break;
	}
	printf("%.1lf",end);
	return 0;
}