#include<stdio.h>
int main()
{
	int a,b,c;
	scanf("%d%d%d",&a,&b,&c);
	printf("%.1f",c-(a+b)*0.9);
	return 0;
}
/**************************************************************
	Problem: 1598
	User: admin
	Language: C
	Result: Accepted
	Time:11 ms
	Memory:1144 kb
****************************************************************/