Petr stands in line of n people, but he doesn't know exactly which position he occupies. He can say that there are no less than a people standing in front of him and no more than b people standing behind him. Find the number of different positions Petr can occupy.

Input

The only line contains three integers n, a and b (0 ≤ a, b < n ≤ 100).

Output

Print the single number — the number of the sought positions.

Examples

Input

3 1 1


Output

2


Input

5 2 3


Output

3

Note

The possible positions in the first sample are: 2 and 3 (if we number the positions starting with 1).

In the second sample they are 3, 4 and 5.
/**
 * Created by iainws on 1/10/2014.
 */

import java.io.InputStreamReader;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.InputStream;

public class TheNumberPositions {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReaderTheNumberPositions in = new InputReaderTheNumberPositions(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskTheNumberPositions solver = new TaskTheNumberPositions();
        solver.solve(1, in, out);
        out.close();
    }
}
class TaskTheNumberPositions {
    public void solve(int taskNumber, InputReaderTheNumberPositions in, PrintWriter out) {
        int n = in.nextInt();
        int a = in.nextInt();
        int b = in.nextInt();
        int res = 0;
        for(int i = 0; i < n;++i){
            int left = n - i - 1;
            if(i <= b && left >= a)res++;
        }
        out.println(res);
    }
}
class InputReaderTheNumberPositions {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public InputReaderTheNumberPositions(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
    }

    public String next() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

}