#include<bits/stdc++.h>
using namespace std;
int x,y,n;
int main(){
cin>>x>>y>>n;
printf("%.1f",n-(x+y)*0.9); 
    return 0;
}
 
/**************************************************************
	Problem: 1598
	User: chenyichuen
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/