#include <cstdio>
#include <cmath>
#include <iostream>

using namespace std;

int a[105];
int n,b,c;

void input() {
    for(int i = 1 ; i <= n ; i ++) scanf("%d",a+i);
    int cnt = 0;
    for(int i = 1 ; i <= n ; i ++) {
        for(int j = i + 1 ; j <= n ;j ++) {
            int tmp = a[i] - a[j];
            if(tmp < 0) tmp = -tmp;
            if(tmp%b == c) cnt ++;
        }
    }
    printf("%d\n",cnt);
}

void solve() {

}

int main(void) {
    //freopen("a.in","r",stdin);
    while(~scanf("%d %d %d",&n,&b,&c)) {
        input();
        solve();
    }
}