using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		if(B - A == 0){
			Console.WriteLine(C);
		} else {
			Console.WriteLine( ( C * (C-B) / (B-A) + (B*B - A*C) / (B-A) ));
		}
	}
	Q A,B,C;
	public Sol(){
		var d = rla();
		A = d[0]; B = d[1]; C = d[2];
	}

	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(char sep=' '){return Console.ReadLine().Split(sep);}
	static int[] ria(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>int.Parse(e));}
	static long[] rla(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>long.Parse(e));}
	static double[] rda(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>double.Parse(e));}
}


struct Q:IComparable<Q> {
	long num;
	long den;
	public static long gcd(long a, long b){
		return a == 0 ? b : gcd(b % a, a);
	}
	public static Q Red(Q x){
		long n = x.Num;
		long d = x.Den;
		long g = gcd(Math.Abs(n), Math.Abs(d));
		n /= g;
		d /= g;
		if(d < 0){n *= -1;d *= -1;}
		return new Q(n, d);
	}
	
	public int CompareTo(Q t){
		var d  =  num * t.den - den * t.num;
		return d > 0 ? 1 : d < 0 ? -1 : 0;
	}
	
	public long Num{
		get{return num;}
		set{this.num = value;}
	}
	public long Den{
		get{return den;}
		set{this.den = value;}
	}
	
	public Q(long n_, long d_){
		if(d_ < 0){ n_ *= -1;d_ *= -1;}
		long g = gcd(Math.Abs(n_), Math.Abs(d_));
		n_ /= g;
		d_ /= g;
		num = n_; den = d_;
	}
	
	public static implicit operator Q(long n){
		return new Q(n, 1);
	}
	public static Q operator+(Q a, Q b){
		 return (new Q(a.Num * b.Den + a.Den * b.Num, a.Den * b.Den));
	}
	public static Q operator-(Q a, Q b){
		 return (new Q(a.Num * b.Den - a.Den * b.Num, a.Den * b.Den));
	}
	public static Q operator-(Q a){
		 return (new Q(-a.Num, a.Den));
	}
	public static Q operator*(Q a, Q b){
		 return (new Q(a.Num * b.Num, a.Den * b.Den));
	}
	public static Q operator/(Q a, Q b){
		 return (new Q(a.Num * b.Den, a.Den * b.Num));
	}
	public static bool operator>(Q a, Q b){
		 return a.CompareTo(b) > 0;
	}
	public static bool operator<(Q a, Q b){
		 return a.CompareTo(b) < 0;
	}
	public static bool operator>= (Q a, Q b){
		 return a.CompareTo(b) >=  0;
	}
	public static bool operator<= (Q a, Q b){
		 return a.CompareTo(b) <=  0;
	}
	
	public static bool operator == (Q a, Q b){
		 return a.Equals(b);
	}
	public static bool operator != (Q a, Q b){
		 return !(a == b);
	}
	
	public override bool Equals(System.Object obj){
		if(obj  ==  null) return false;
		Q p  =  (Q) obj;
		if((System.Object) p  ==  null) return false;
		return den * p.num  ==  num * p.den;
	}
	public override int GetHashCode(){
		return (den ^ num).GetHashCode();
	}
	
	
	public static Q Min(Q a, Q b){
		 return a < b ? a : b;
	}
	public override String ToString(){
		return this.Num.ToString()+"/"+this.Den.ToString();
	}
}