#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,y,n;
	cin>>x>>y>>n;
	printf("%.1f",n-((x+y)*0.9));
	
}
/**************************************************************
	Problem: 1598
	User: baizhoudeyueguang
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/