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

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