#include<bits/stdc++.h>
using namespace std;
int main(){
	float x,y,n,z;
	cin>>x>>y>>n;
	z=n-(x+y)*0.9;
	printf("%.1f",z);
}
/**************************************************************
	Problem: 1598
	User: tonghuatao
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/