import java.util.Scanner;
public class B {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int A = scanner.nextInt();
int B = scanner.nextInt();
int X = scanner.nextInt();
int cups = 0;
int balanceA = 0;
int tempA = A;
int lostA = 0;
while (tempA >= 1){
tempA--;
lostA++;
balanceA += 500;
if (balanceA >= X){
balanceA = 0;
cups++;
A = A - lostA;
lostA = 0;
}
}
int balanceB = 0;
int tempB = B;
int lostB = 0;
while (tempB >= 1){
tempB--;
lostB++;
balanceB += 1000;
if (balanceB >= X){
balanceB = 0;
cups++;
B = B - lostB;
lostB = 0;
}
}
int commonBalance = 0;
while (B >= 1 && A >= 1){
B--;
A--;
commonBalance += 1500;
if (commonBalance >= X){
commonBalance = 0;
cups++;
}
}
System.out.println(cups);
}
}