include <bits/stdc++.h>

using namespace std;

int main() {

int n, z, x, w;
cin >> n >> z >> x;
int u = min(min(n - z + 1, n - x + 1), min(z, x));
int h = 0;

for (int q = 1; q < u; q++) {

	int t = n - 2 * q + 2;
	int y = n - 2 * q;
	h += (t * t - y * y);
}

h++;

if (u == z) {
	h += (x - u);
	cout << h;
	return 0;
}

h += (n - 2 * (u - 1));

if (u == n - x + 1) {
	h += (z - u);
	return 0;
}

h += (n - 2 * (u - 1));

if (u == n - z + 1) {
	h += (n - 2 * (u - 1)) - (x - u);
	return 0;
}

h += (n - 2 * (u - 1));
cout << h + (n - 2 * (u - 1)) - (z - u);
return 0;

}