Медианчо

#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <unordered_map>
using namespace std;

int main()
{
    int n,b;
    cin >> n >>b;
    vector<int>nums(n+1);


    int whereM=-1;
    for(int i=1; i<=n; i++)
    {
        int x;
        cin>>x;

        if(x==b)
        {
            whereM=i;
        }
        nums[i]=x;
    }
    int sum=0;
    unordered_map<int,int> odd;

    unordered_map<int,int> even;
    even[0]=1;
    odd[0]=0;
    for(int i=whereM-1; i>0; i--)
    {
        if(nums[i]>b)sum++;
        else  sum--;
        if((whereM-i)%2==0)
        {
            if(even.find(sum)!=even.end())even[sum]++;
            else even[sum]=1;
        }
        else if(odd.find(sum)!=odd.end())odd[sum]++;
        else odd[sum]=1;
    }

    sum=0;
    int count=even[0];
    for(int i=whereM+1; i<=n ; i++)
    {
        if(nums[i]>b)sum++;
        else sum--;
        if((i-whereM)%2==0)
        {
            if(even.find(-sum)!=even.end())   count +=even[-sum];
        }

        else
        {
            if(odd.find(-sum)!=odd.end())   count+=odd[-sum];
        }
    }

    cout << count<<'\n';
    return 0;
}