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

}

/**************************************************************
	Problem: 1597
	User: huangluowei
	Language: C++
	Result: Wrong Answer
****************************************************************/