#include <stdio.h>
#include <math.h>
#include <iostream>
using namespace std;
int data[101], n, b, c;
bool judge(int i, int j)
{
    if (abs(data[i]-data[j])%b == c) return true;
    return false;
}
int main()
{
    int i, j, ret;
    while (scanf("%d%d%d", &n, &b, &c) != EOF)
    {
        for (i = 0; i < n; i++) scanf("%d", &data[i]);
        for (i = 0, ret = 0; i < n; i++)
            for (j = i+1; j < n; j++)
                if (judge(i, j)) ret++;
        printf("%d\n", ret);
    }
}