/*
  PROB:BC #63 t1 
  TIME:151121 eve
*/
//  #define me AcrossTheSky
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <iostream>
#include <cmath>
#include <vector>
#include <set>
#include <string>
using namespace std;
int a[1000];

int main(){
    int n,b,c;
    while (scanf("%d%d%d",&n,&b,&c)!=EOF){
        for (int i=1;i<=n;i++) scanf("%d",&a[i]);
        int ans=0;
        for (int i=1;i<=n;i++)
            for (int j=i+1;j<=n;j++) if (abs(a[i]-a[j])%b==c) ans++;
            
        cout << ans << endl;
    }
}