#include <bits/stdc++.h>
using namespace std;
int main() {
	float x,y,n,a;
	scanf("%f %f %f",&x,&y,&n);
	a=n-(x+y)*0.9;
	printf("%.1f",a);
} 
/**************************************************************
	Problem: 1598
	User: toughuatao1
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/