#include<bits/stdc++.h>
using namespace std;
int n,x,y;
int main(){
	cin>>x>>y>>n;
	cout<<fixed<<setprecision(1)<<n-(x+y)*0.9;
}
/**************************************************************
	Problem: 1598
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/