import java.util.*;

public class Main {
    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 dx=0;
        int dy=0;
        if(d>x){dx=d-x;}
        if(d>y){dy=d-y;}
        int ans=d+1-dx-dy;
        if(ans<0){ans=0;}
        System.out.println(ans);
    }
}