Little Elephant and Array

#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

const int N(100001);
typedef pair<int,int> II;

int main(){
    vector<int> lv[N];
    vector<pair<II,int>> arr;
    int n, q, a, b, v, g;
    g = scanf("%d %d", &n, &q);
    for(int i = 1; i <= n; ++i){
        g = scanf("%d", &v);
        if(v > n) continue;
        lv[v].push_back(i);
    }
    int round[] = {1, -2, 1};
    for(int i = 1; i <= n; ++i){
        for(int k = 0; k <= 2; ++k){
            int l = 0, r = i + k - 1;
            while(r < (int)lv[i].size())
                arr.push_back(make_pair(II(lv[i][l++], lv[i][r++]), round[k]));
        }
    }
    sort(arr.begin(), arr.end());
    for(int t = 0; t < q; ++t){
        g = scanf("%d %d", &a, &b);
        int cnt = 0;
        auto x = lower_bound(arr.begin(), arr.end(), make_pair(II(a, -1), -1));
        while(x != arr.end() and (x->first).first <= b){
            if((x->first).second <= b) cnt += x->second;
            x++;
        }
        printf("%d\n", cnt);
    }
    return 0;
}