#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int maxn = 155;
int a[maxn];
int main()
{
    int n,b,c,ans;
    ///freopen("in.txt","r",stdin);
    while(scanf("%d%d%d",&n,&b,&c)!=EOF){
        ans = 0;
        for(int i = 0;i<n;i++)scanf("%d",&a[i]);
        for(int i = 0;i<n;i++)
        for(int j = i+1;j<n;j++){
            if(abs(a[i]-a[j])%b==c)ans++;
        }
        printf("%d\n",ans);
    }
    return 0;
}