Arpa’s obvious problem and Mehrdad’s terrible solution

#include <iostream>
#include <map>
#include <cstring>
using namespace std;
long long m[100001];

int main() {
    int n,x,r,aux;
    long long ans=0;

    //map<long long,long long>m;

    cin>>n>>x;
    memset(m,0,sizeof(m));
    while(n--){
        cin>>r;
        aux=r^x;
        ans=ans+m[aux];
        m[r]++;
    }
    cout<<ans<<endl;
    return 0;
}