显然莫队。

莫队，易得

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;

int blo = 320;

int bel[N];
int cnt[N];
int ans = 0;
int a[N], n, m;
vector<int> b;
int rn[N];
int res[N];

struct Query
{
	int l, r, id;
	bool operator<(const Query& g) const
	{
		return ((bel[l] ^ bel[g.l]) ? (bel[l] < bel[g.l]) : ((bel[l] & 1) ? (r < g.r) : (r > g.r)));
	}
}q[N];

void del(int x)
{
	int p = a[x];
	int np = rn[p];
	ans -= (cnt[p] == np);
	cnt[p]--;
	ans += (cnt[p] == np);
}

void add(int x)
{
	int p = a[x];
	int np = rn[p];
	ans -= (cnt[p] == np);
	cnt[p]++;
	ans += (cnt[p] == np);
}

int main()
{
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= n; i++) scanf("%d", &a[i]), b.emplace_back(a[i]), bel[i] = i / blo;
	sort(b.begin(), b.end());
	b.erase(unique(b.begin(), b.end()), b.end());
	for (int i = 1; i <= n; i++)
	{
		int pn = a[i];
		a[i] = lower_bound(b.begin(), b.end(), a[i]) - b.begin() + 1;
		rn[a[i]] = pn;
	}
	for (int i = 1; i <= m; i++)
	{
		scanf("%d%d", &q[i].l, &q[i].r);
		q[i].id = i;
	}
	sort(q + 1, q + m + 1);
	int nl(1), nr(0);
	for (int i = 1; i <= m; i++)
	{
		int l(q[i].l), r(q[i].r);
		while (nl > l) add(--nl);
		while (nr < r) add(++nr);
		while (nl < l) del(nl++);
		while (nr > r) del(nr--);
		res[q[i].id] = ans;
	}
	for (int i = 1; i <= m; i++) printf("%d\n", res[i]);
	return 0;
}