#include "map"
#include "stack"
#include "queue"
#include "vector"
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "iostream"
#include "algorithm"
using namespace std;
#define N 100005
#define eps 1e-8
#define inf 0x7ffffff
#define pi 3.1415926535897932384626433832795028841971
typedef long long LL;
int main()
{
    LL n,b,c,i,sum,j;
    LL a[1111];
    while(~scanf("%lld%lld%lld",&n,&b,&c))
    {
        for(i=0;i<n;i++)
            scanf("%lld",&a[i]);
        sum=0;
        for(i=0;i<n-1;i++)
        {
            for(j=i+1;j<n;j++)
            {
                if(abs(a[i]-a[j])%b==c)
                    sum++;
            }
        }
        printf("%lld\n",sum);
    }
    return 0;
}