#include <iostream>
#include <algorithm>

int main() {
    int a, b, c;
    std::cin >> a >> b >> c;

    int arr[3] = {a, b, c};
    std::sort(arr, arr + 3);

    int trepte_libere = (arr[1] - arr[0] - 1) + (arr[2] - arr[1] - 1);

    std::cout << trepte_libere << std::endl;
    return 0;
}