#include<bits/stdc++.h>
using namespace std;
int main(){
	float x,y,n,a,j;
	cin>>x>>y>>n;
	a=(x+y)*0.9;
	j=n-a;
	printf("%.1f",j);
}
/**************************************************************
	Problem: 1598
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/