#include <cstdio>
int a[10000];
int abs(int x)
{
    return x > 0 ? x : -x;
}
int main()
{
    int n,b,c;
    while (scanf("%d%d%d",&n,&b,&c) != EOF)
    {
        int ans = 0;
        for (int i = 1;i <= n;i++)
            scanf("%d",&a[i]);
        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);
    }
}