#include<cstdio>
#include<algorithm>

using namespace std;

int n,b,c,a[1010],ans;

int main()
{
    while(scanf("%d%d%d",&n,&b,&c)!=EOF)
    {
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
        ans=0;
        for(int i=1;i<=n;i++)
            for(int j=i+1;j<=n;j++)
                if(abs(a[j]-a[i])%b==c)ans++;
        printf("%d\n",ans);
    }
}