dsu

#include "bits/stdc++.h"

using namespace std;

const int maxN = 1e5 + 10;
int p[maxN],r[maxN];
bool has[maxN];

int __find__ (int a) {
	return p[a] = (p[a] == a ? a : __find__(p[a]));
}

void __union__ (int a,int b) {
	a = __find__(a);
	b = __find__(b);
	if (r[a] == r[b]) ++r[a];
	if (r[a] > r[b]) p[b] = a;
	else p[a] = b;
}

int main () {
	 ios::sync_with_stdio(false);
	 cin.tie(nullptr);
	 cout.tie(nullptr);
	 int n, m;
	 cin >> n >> m;
	 for (int i = 1; i <= n; ++i) p[i] = i;
	 for (int i = 1; i <= m; ++i) {
		 int u, v;
		 cin >> u >> v;
		 __union__(u, v);
	 }
	 int cnt[n + 1];
	 fill(cnt, cnt + n + 1, 0);
	 for (int i = 1; i <= n; ++i) {
		 cnt[__find__(i)]++;
	 }
	 int cc = 0;
	 for (int i = 1; i <= n; ++i) {
		 if (cnt[i] > 0) ++cc;
	 }
	 cout << cc << '\n';
}