// Exported by Exporter.exe

// Included from A.cpp
// Compile flags -Wall -Wextra -Wshadow -D_GLIBCXX_ASSERTIONS -DDEBUG -ggdb3 -fmax-errors=2
#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define F first
#define S second
#define MP make_pair
#define MTP make_tuple
#define R Read
#define RD Read_Digit
#define RP Read_P
#define RL Read_Loop
#define RLD Read_Loop_Digit
#define RLP Read_Loop_P
typedef long long int ll;
typedef unsigned long long int ull;

constexpr int kN = int(1E5 + 10);
// constexpr int kMod = 998244353;
// constexpr int kMod = int(1E9 + 7);
// constexpr int kInf = 0x3f3f3f3f;
// constexpr ll kInf = 0x3f3f3f3f3f3f3f3f;
// constexpr double kPi = acos(-1);
// constexpr double kEps = 1E-9;



// Included from C:\Users\ianli\Desktop\CP\template\Various\Fast_IO\Fast_IO.cpp
// --- Get ---
static inline char Get_Raw_Char() {
	static char buf[1 << 16], *p = buf, *end = buf;
	if (p == end) {
		if ((end = buf + fread(buf, 1, 1 << 16, stdin)) == buf) return '\0';
		p = buf;
	}
	return *p++;
}

static inline int Get_Digit() {
	char c = Get_Raw_Char();
	while (!isdigit(c)) c = Get_Raw_Char();
	return int(c - '0');
}

template <typename T> static inline int Get_P() {
	static_assert(is_integral<T>::value);
	char c = Get_Raw_Char();
	while (!isdigit(c)) c = Get_Raw_Char();
	T ret = int(c - '0');
	while (isdigit(c = Get_Raw_Char())) ret = ret * 10 + int(c - '0');
	return ret;
}

template <typename T> static inline int Get() {
	static_assert(is_integral<T>::value);
	char c = Get_Raw_Char();
	bool neg = false;
	while (!isdigit(c)) {
		if (c == '-') neg = true;
		c = Get_Raw_Char();
	}
	T ret = int(c - '0');
	while (isdigit(c = Get_Raw_Char())) ret = ret * 10 + int(c - '0');
	if (neg) return -ret;
	return ret;
}

// --- Read ---
template <typename T> static inline void Read_P(T &n) {
	static_assert(is_integral<T>::value);
	char c = Get_Raw_Char();
	while (!isdigit(c)) c = Get_Raw_Char();
	n = int(c - '0');
	while (isdigit(c = Get_Raw_Char())) n = n * 10 + int(c - '0');
	return ;
}

template <typename T> static inline void Read(T &n) {
	static_assert(is_integral<T>::value);
	char c = Get_Raw_Char();
	bool neg = false;
	while (!isdigit(c)) {
		if (c == '-') neg = true;
		c = Get_Raw_Char();
	}
	n = int(c - '0');
	while (isdigit(c = Get_Raw_Char())) n = n * 10 + int(c - '0');
	if (neg) n = -n;
	return ;
}

template <typename T> static inline void Read_Digit(T &n) {
	static_assert(is_integral<T>::value);
	char c = Get_Raw_Char();
	while (!isdigit(c)) c = Get_Raw_Char();
	n = int(c - '0');
	return ;
}

// --- Read multiple ---
template <typename T, typename... Targs> static inline void Read(T &n, Targs&... Fargs) {
	Read(n);
	return Read(Fargs...);
}

template <typename T, typename... Targs> static inline void Read_Digit(T &n, Targs&... Fargs) {
	Read_Digit(n);
	return Read_Digit(Fargs...);
}

template <typename T, typename... Targs> static inline void Read_P(T &n, Targs&... Fargs) {
	Read_P(n);
	return Read_P(Fargs...);
}

// --- Read Loop ---
template <typename T> static inline void Read_Loop_i(int i, T *a) {return Read(a[i]);}
template <typename T, typename... Targs> static inline void Read_Loop_i(int i, T *a, Targs*... Fargs) {
	Read(a[i]);
	return Read_Loop_i(i, Fargs...);
}
template <typename... Targs> static inline void Read_Loop(int n, Targs*... Fargs) {
	for (int i = 1; i <= n; i++) Read_Loop_i(i, Fargs...);
	return ;
}

template <typename T> static inline void Read_Loop_Digit_i(int i, T *a) {return Read_Digit(a[i]);}
template <typename T, typename... Targs> static inline void Read_Loop_Digit_i(int i, T *a, Targs*... Fargs) {
	Read_Digit(a[i]);
	return Read_Loop_Digit_i(i, Fargs...);
}
template <typename... Targs> static inline void Read_Loop_Digit(int n, Targs*... Fargs) {
	for (int i = 1; i <= n; i++) Read_Loop_Digit_i(i, Fargs...);
	return ;
}

template <typename T> static inline void Read_Loop_P_i(int i, T *a) {return Read_P(a[i]);}
template <typename T, typename... Targs> static inline void Read_Loop_P_i(int i, T *a, Targs*... Fargs) {
	Read_P(a[i]);
	return Read_Loop_P_i(i, Fargs...);
}
template <typename... Targs> static inline void Read_Loop_P(int n, Targs*... Fargs) {
	for (int i = 1; i <= n; i++) Read_Loop_P_i(i, Fargs...);
	return ;
}

// --- Float ---

template <int mul, typename T> static inline void Read(T &n) {
	char c = Get_Raw_Char();
	bool neg = false;
	while (!isdigit(c)) {
		if (c == '-') neg = true;
		c = Get_Raw_Char();
	}
	n = int(c - '0');
	while (isdigit(c = Get_Raw_Char())) n = n * 10 + int(c - '0');
	
	int cnt = 0;

	if (c == '.') {
		while (isdigit(c = Get_Raw_Char())) {
			n = n * 10 + int(c - '0');
			cnt++;
		}
	}

	while (cnt < mul) {
		n = n * 10;
		cnt++;
	}

	if (neg) n = -n;
	return ;
}

template <int mul, typename T> static inline void Read_P(T &n) {
	char c = Get_Raw_Char();
	while (!isdigit(c)) c = Get_Raw_Char();
	
	n = int(c - '0');
	while (isdigit(c = Get_Raw_Char())) n = n * 10 + int(c - '0');
	
	int cnt = 0;

	if (c == '.') {
		while (isdigit(c = Get_Raw_Char())) {
			n = n * 10 + int(c - '0');
			cnt++;
		}
	}

	while (cnt < mul) {
		n = n * 10;
		cnt++;
	}
	return ;
}

template <int mul, typename T, typename... Targs> static inline void Read(T &n, Targs&... Fargs) {
	Read<mul>(n);
	return Read<mul>(Fargs...);
}

template <int mul, typename T, typename... Targs> static inline void Read_P(T &n, Targs&... Fargs) {
	Read_P<mul>(n);
	return Read_P<mul>(Fargs...);
}

// --- cin, cout ---
void IOS() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	return ;
}

// --- freopen ---
void Freopen(const char *in, const char *out) {	
	freopen(in, "r", stdin);
	freopen(out, "w", stdout);
	return ;
}

// --- Output __int128 ---

template <typename T> void Print128(T x) {
	if (x < 0) {
		printf("-");
		x = -x;
	}
	if (x == 0) printf("0");
	else {
		static int val[100];
		int idx = -1;
		while (x) {
			val[++idx] = x % 10;
			x /= 10;
		}
		while (idx >= 0) printf("%d", val[idx--]);
	}
} 

// End of C:\Users\ianli\Desktop\CP\template\Various\Fast_IO\Fast_IO.cpp


// Included from C:\Users\ianli\Desktop\CP\template\Various\Useful_Functions\Useful_Functions.cpp
// --- sort ---
template <typename T> inline void sort(vector<T> &v) {return sort(v.begin(), v.end());}
template <typename T> inline void sort(int n, T *a) {return sort(a + 1, a + n + 1);}
template <typename T> inline void sort_r(vector<T> &v) {return sort(v.begin(), v.end(), greater<T>());}
template <typename T> inline void sort_r(int n, T *a) {return sort(a + 1, a + n + 1, greater<T>());}

// --- Merge ---
template <typename T> inline void Merge_Vec(vector<T> &a, vector<T> &b, vector<T> &c) {
	if (c.size() < a.size() + b.size()) c.resize(a.size() + b.size());
	merge(a.begin(), a.end(), b.begin(), b.end(), c.begin());
	return ;
}

// --- Discrete ---
template <typename T> inline void Discrete(vector<T> &v) {
	sort(v);
	v.resize(unique(v.begin(), v.end()) - v.begin());
	return ;
}

// --- Relabel ---
template <typename T> inline void relabel(int n, T *val, T *dist) {
	if (!dist) dist = val;
	T *tmp = new T[n + 1];
	memcpy(tmp, val, sizeof(T) * (n + 1));
	sort(n, tmp);
	int sz = unique(tmp + 1, tmp + n + 1) - (tmp + 1);
	for (int i = 1; i <= n; i++) dist[i] = lower_bound(tmp + 1, tmp + sz + 1, val[i]) - tmp;
	delete tmp;
	return ;
}

// --- PQ ---
template <typename T> using PQ = priority_queue<T>;
template <typename T> using PQ_R = priority_queue<T, vector<T>, greater<T>>;

// --- misc ---

template <typename T> T ABS(T n) {return n >= 0 ? n : -n;}
template <typename T> T gcd(T a, T b) {return b ? gcd(b, a % b) : a;}
template <typename T> T lcm(T a, T b) {return a * b / gcd(a, b);}
template <typename T> T mex(T a, T b) {return (a == 0 || b == 0) ? ((a == 1 || b == 1) ? 2 : 1) : 0;}
// End of C:\Users\ianli\Desktop\CP\template\Various\Useful_Functions\Useful_Functions.cpp


// Included from C:\Users\ianli\Desktop\CP\template\Various\Debug\Debug.cpp
void print(const int &x) {printf("%d", x);}
void print(const long long int &x) {printf("%lld", x);}
void print(const double &x) {printf("%.20lf", x);}
void print(const char *x) {printf("%s", x);}

void print(const int n, const int *x) {
	printf("%d", x[1]); for (int i = 2; i <= n; i++) printf(" %d", x[i]); printf("\n");
	return ;
}

void print(const int n, const long long int *x) {
	printf("%lld", x[1]); for (int i = 2; i <= n; i++) printf(" %lld", x[i]); printf("\n");
	return ;
}
// End of C:\Users\ianli\Desktop\CP\template\Various\Debug\Debug.cpp


int main() {
	int a, b, c, d; R(a, b, c, d);
	if (a == c || b == d || ABS(a - c) + ABS(b - d) <= 3) printf("1\n");
	else printf("2\n");
}
// End of A.cpp