#include<bits/stdc++.h>
using namespace std;
int main() {
	int x,y,n;
	float s;
	cin>>x>>y>>n;
 	s=n-((x+y)*0.9);
	printf("%.1f",s);
} 
/**************************************************************
	Problem: 1598
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/