import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner (System.in);
		int n = sc.nextInt();
		int a = sc.nextInt();
		int x = sc.nextInt();
		System.out.print(qingWa(n,a,x));
		
	}
	public static int qingWa(int a,int b,int c) {
		int n = a - b * c;
		
		return n;
	
	}

}
/**************************************************************
	Problem: 1599
	User: admin
	Language: Java
	Result: Accepted
	Time:788 ms
	Memory:40200 kb
****************************************************************/