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;
		int lim;
		int xst;
		
		if ((d-y1) < 0) {
			lim = 0;
		} else {
			lim = d-y1;
		}
		
		if (x1 < d) {
			xst = x1;
		} else {
			xst = d;
		}
		
		if (d > (x1+y1)) {
		} else if (d==(x1+y1)) {
			ans = 1;
		} else {
			for (x=xst;x>=lim;x--) {
				if ((d-x)>=0 && y1>=(d-x)) {
					ans++;
				}
			}
		}
		System.out.println(ans);		
	}
}