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