#include<bits/stdc++.h>
using namespace std;
int main() {
	float x,y,n,f;
	cin>>x>>y>>n;
	f=n-(x+y)*0.9;
	cout<<f;
    return 0;
}

/**************************************************************
	Problem: 1598
	User: huangcanwu
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/