[BZOJ1529][POI2005]ska Piggy banks

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <stack>
#include <vector>
#include <queue>
#include <cstring>
#include <string>
#include <map>
#include <set>
using namespace std;

const int BufferSize = 1 << 16;
char buffer[BufferSize], *Head, *Tail;
inline char Getchar() {
	if(Head == Tail) {
		int l = fread(buffer, 1, BufferSize, stdin);
		Tail = (Head = buffer) + l;
	}
	return *Head++;
}
int read() {
	int x = 0, f = 1; char c = Getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = Getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = Getchar(); }
	return x * f;
}

#define maxn 1000010
int n, fa[maxn], pos[maxn];
int findset(int x) { return x == fa[x] ? x : fa[x] = findset(fa[x]); }

int main() {
	n = read();
	for(int i = 1; i <= n; i++) fa[i] = i;
	for(int i = 1; i <= n; i++) {
		int u = findset(i), v = findset(read());
		if(u != v) fa[v] = u;
	}
	
	for(int i = 1; i <= n; i++) pos[i] = findset(i);
	sort(pos + 1, pos + n + 1);
	
	int cnt = 0;
	for(int i = 1; i <= n; i++) if(i == 1 || pos[i] != pos[i-1]) cnt++;
	printf("%d\n", cnt);
	
	return 0;
}