#include<iostream>
#include<math.h>
using namespace std;


int num[1000];

int main() {
    int n, b, c;
    int re = 0;
    while (scanf("%d %d %d", &n, &b, &c) != EOF) {
        for (int i = 1; i <= n; i++) scanf("%d", &num[i]);
        re = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = i + 1; j <= n; j++) {
                if (abs(num[i] - num[j]) % b == c)
                    re++;
            }
        }
        cout << re << endl;
    }
    return 0;

}