#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,y;
	float n,d,a;
	cin>>x>>y>>n;
	a=x+y;
	d=n-a*0.9;
	printf("%.1f",d);
	
}

/**************************************************************
	Problem: 1598
	User: zhengzihao3
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/