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 x = nint[0];
		int y = nint[1];
		int d = nint[2];
		int ans = 0;
		int flags = 0;
		
		if (d>x+y) {
			flags ++;
		} 
		
		int xmax = 0;
		int xmin = 0;
		
		if (d<=x) {
			xmax = d;
		} else if (d>x) {
			xmax = x;
		}
		
		if (d>y) {
			xmin = d-y;
		} else if (d<=y) {
			xmin = 0;
		}
		
		if (flags == 0) {
			ans = xmax - (xmin - 1);
		}
		
		System.out.println(ans);		
	}
}