import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.bigint, std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static File _f;
void file_io(string fn) { _f = File(fn, "r"); }
static string[] s_rd;
T _RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T _RD(T = long)(File f) { while(!s_rd.length) s_rd = f.readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T[] _RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[] _RDA(T = long)(File f, T fix = 0) { auto r = f.readln.chomp.split.to!(T[]); r[] += fix; return r; }
T RD(T = long)() { if (_f.isOpen) return _RD!T(_f); else return _RD!T; }
T[] RDA(T = long)(T fix = 0) { if (_f.isOpen)  return _RDA!T(_f, fix); else return _RDA!T(fix); }

size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

void chmin(T)(ref T x, T y) { x = min(x, y); } void chmax(T)(ref T x, T y) { x = max(x, y); }
bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
T lcm(T)(T x, T y) { return x * (y / gcd(x, y)); }

long mod = 10^^9 + 7;
//long mod = 998_244_353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }
void modpow(ref long x, long y) { if (!y) { x = 1; return; } auto t = x; x.modpow(y>>1); x.modm(x); if (y&1) x.modm(t); }
void modd(ref long x, long y) { y.modpow(mod - 2); x.modm(y); }

struct UnionFind(T)
{
	void init(T n) { par = new T[](n); foreach (i; 0..n) par[i] = i; cnt = new T[](n); fill(cnt, 1); }
	T root(T i) { return par[i] == i ? i : (par[i] = root(par[i])); }
	bool same(T i, T j) { return root(i) == root(j); }
	void unite(T i, T j) { i = root(i); j = root(j); if (i == j) return; par[i] = j; cnt[j] += cnt[i]; }
	T size(T i) { return cnt[root(i)]; }
	T[] par, cnt;
}

void main()
{
	auto N = RD;
	auto M = RD;
	auto pos = new long[][](N);
	foreach (i; 0..N)
	{
		auto b = RD-1;
		auto c = RD-1;
		pos[c] ~= b;
	}

	UnionFind!long uf;
	uf.init(N);
	foreach (e; pos)
	{
		if (e.empty) continue;
		foreach (ee; e[1..$])
		{
			uf.unite(e[0], ee);
		}
	}

	auto size = new long[](N);
	foreach (i; 0..N)
	{
		auto root = uf.root(i);
		size[root] = uf.cnt[root] - 1;
	}
	auto ans = size.sum;

	writeln(ans);
	stdout.flush;
	debug readln;
}