#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: lvrenxiang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/