#pragma region template
// clang-format off

#if __has_include(<src.hpp>)
#include <src.hpp>  // precompiled header
#endif

#if (defined __INTELLISENSE__) && (!defined PROPER)
#define NDEBUG
namespace std {
#endif

#include <cassert>
#include <cctype>
#include <cmath>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

#if (defined __INTELLISENSE__) && (!defined PROPER)
  using namespace std;
}
#endif

#ifdef LOCAL_DEBUG
#include <debugger.hpp>  // https://gist.github.com/naskya/2c5c84dbc8f70a2e5680b4267fff1af5
#define see(...) debugger::print(#__VA_ARGS__, __VA_ARGS__)
#define here(label) debugger::output << "[Debug] " << #label << (std::string(#label).empty() ? "" : " | ") << "line " << __LINE__ << " (" << __func__ << ")\n"
#define trace(label, ...) do {here(label); see(__VA_ARGS__);} while(0)
#define com(msg) debugger::output << "[Debug] " << msg << "\n"
#define local(x) do {x} while(0)
#define alter(x, y) x
#else
#define see(...) (static_cast<void>(0))
#define here(label) (static_cast<void>(0))
#define trace(label, ...) (static_cast<void>(0))
#define com(msg) (static_cast<void>(0))
#define local(x) (static_cast<void>(0))
#define alter(x, y) y
#endif

#if (!defined LOCAL_DEBUG) || (defined NOWARN)
#define warn(msg) (static_cast<void>(0))
#else
#define warn(msg) debugger::output << "[Warning] " << msg << "\n"
#endif

#if (defined LOCAL_DEBUG) || (defined LOCAL_NDEBUG) || (defined __INTELLISENSE__)
#define NOEXCEPT
#define M_assert(expr) assert(expr)
#define O_assert(expr) assert(expr)
#else
#define NOEXCEPT noexcept
#define M_assert(expr) do {if(__builtin_expect(!(expr), 0)) {long long *p = (long long*) std::malloc(1 << 30); for (int i = 0; i < static_cast<int>((1 << 30) / sizeof(long long)); p[i] = 1, i += (1 << 9)); std::fprintf(stderr, "%lld", *p);}} while(0)
#define O_assert(expr) do {if(__builtin_expect(!(expr), 0)) for(int i = 0; i < (1 << 24); i++) std::puts("Hello, world!");} while(0)
#endif

#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rng(i, f, t, s) for (int i = (f); ((s) > 0) ? (i < (int)(t)) : (i > (int)(t)); i += (s))
#define erng(i, f, t, s) for (int i = (f); ((s) > 0) ? (i <= (int)(t)) : (i >= (int)(t)); i += (s))

[[maybe_unused]] constexpr int         INF   = 1000000005;
[[maybe_unused]] constexpr long long   LINF  = 1000000000000000005LL;
[[maybe_unused]] constexpr double      EPS   = 1e-9;
[[maybe_unused]] constexpr long double LEPS  = 1e-14L;
[[maybe_unused]] constexpr int         dy[9] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
[[maybe_unused]] constexpr int         dx[9] = {0, 1, 0, -1, -1, 1, 1, -1, 0};

template <class S, class T, class... U, class V = std::common_type_t<S, T, U...>> constexpr V Min(const S a, const T b, const U... c) {
  if constexpr (sizeof...(U)) return std::min((V) a, (V) Min(b, c...)); else return std::min((V) a, (V) b);
}
template <class S, class T, class... U, class V = std::common_type_t<S, T, U...>> constexpr V Max(const S a, const T b, const U... c) {
  if constexpr (sizeof...(U)) return std::max((V) a, (V) Max(b, c...)); else return std::max((V) a, (V) b);
}

// clang-format on
#pragma endregion

void solve() {
  int a, b, c, d;
  std::cin >> a >> b >> c >> d;
  c -= a;
  d -= b;

  c = (c < 0) ? -c : c;
  d = (d < 0) ? -d : d;

  if (c == 0 && d == 0)
    std::cout << 0 << "\n";
  else if (c == 0 || d == 0 || (c + d) <= 3)
    std::cout << 1 << "\n";
  else
    std::cout << 2 << "\n";
}

int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  solve();
}