#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: xuezihong1
	Language: C
	Result: Compile Error
****************************************************************/