#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c;
	float s,h;
	cin>>a>>b>>c;
	h=(a+b)*0.9;
	s=c-h; 
	printf("%.1lf",s);
} 
/**************************************************************
	Problem: 1598
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/