#include <iostream>
#include <cmath>
#include <algorithm>
#include <vector>

using namespace std;

int main(){
    int n, a, b, cnt = 0;
    cin >> n >> a >> b;    
    for(int i = 1; i <= n; ++i){
        if(i > a && i >= n - b) ++cnt;
    }
    cout << cnt;
    return 0;
}