#include<bits/stdc++.h>
using namespace std;
int main(){
    float x,y,n,a,j;
    cin>>x>>y>>n;
    a=(x+y)*0.9;
    j=n-a;
    printf("%.1f",j);
}
/**************************************************************
	Problem: 1598
	User: huanglingkai
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/