#include<bits/stdc++.h>
using namespace std;

int main(){
	int x,y,n;
    cin>>x>>y>>n;
	printf("%.1f",n-(x+y)*0.9); 
	return 0;
}

/**************************************************************
	Problem: 1598
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/