#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: lyy002
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/