#include<stdio.h>
#include<cmath>
int main()
{
    long long n,i,j,a[10001],b,c,ans,x,y;
    while (scanf("%I64d",&n)!=EOF)
    {
        ans=0;
        scanf("%I64d%I64d",&b,&c);
        for (i=1;i<=n;i++) scanf("%I64d",&a[i]);
        for (i=1;i<=n;i++)
            for (j=i+1;j<=n;j++)
            {
                if (a[i]<a[j]) {x=a[j]; y=a[i]; }
                else {x=a[i]; y=a[j];}
                if ((x-y)%b==c) ans++;
            }
        printf("%I64d\n",ans);
    }
}