import java.io.*;
import java.util.*;

class Main {
	
	public static void out (Object o) {
		System.out.println(o);
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = 
			new BufferedReader(new InputStreamReader(System.in));
		
		String[] line = br.readLine().split(" ");
		int x = Integer.parseInt(line[0]);
		int y = Integer.parseInt(line[1]);
		int d = Integer.parseInt(line[2]);
		
		int yMax = d;
		int yMin = x < d ? d - x : 0;
		yMax = Math.min(yMax , y);
		
		int ans = yMax - yMin + 1;
		
		out(ans < 0 ? 0 : ans);
	}
}