#include <iostream>
#include <cmath>
#include <cstdio>
#include <algorithm>
#define LL long long
using namespace std;
const int maxn = 1000+10;
int a[maxn];
int main()
{
    int n,b,c;
    while(scanf("%d%d%d\n",&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++;
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}