import java.util.Scanner;

public class No_103 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int d = sc.nextInt();
		int count = 0;
		for (int i = 0; i <= x; i++) {
			if(i > d) continue;
			int dis = d -i;
			for (int j = 0; j <= x; j++) {
						if (j == dis){
							count += 1;
							continue;
						}
			}
		}
		System.out.println(count);
	}

}