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

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] first = br.readLine().split(" ", 3);
        int x = Integer.parseInt(first[0]);
        int y = Integer.parseInt(first[1]);
        int d = Integer.parseInt(first[2]);
        if (x + y < d) {
            System.out.println(0);
            return;
        }
        int x1 = Math.min(d, x);
        int x2 = Math.max(0, d - y);
        System.out.println(Math.abs(x1 - x2) + 1);
    }
}