import java.util.Scanner;

public class P131 {
	public static void main(String args[]) {
		
		Scanner sc = new Scanner(System.in);
		String n = sc.nextLine();
		String[] nstrs = n.split(" ");
		int nint[] = new int[3];
		
		for (int a=0;a<3;a++) {
			nint[a] = Integer.parseInt(nstrs[a]);
		}
		
		int x1 = nint[0];
		int y1 = nint[1];
		int d = nint[2];
		int x;
		int ans = 0;
		
		if (d >= (x1+y1)) {
		} else {
			for (x=d;x>=(d-y1);x--) {
				if ((d-x)>=0 && y1>=(d-x)) {
					ans++;
				}
			}
		}
		System.out.println(ans);		
	}
}