#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP(i,n,0)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 100000000

typedef long long ll;

int main() {
    int i, j, n, d, t;
    int x[i];
    ll ans;
    cin >> n >> d >> t;
    rep (i,n) cin >> x[i];
    ans = n * (2*t+1);
    rep (i,n) rep (j,i) {
        int diff = abs(x[i]-x[j]);
        if (diff%d == 0 && diff/d <= 2*t)
            ans -= 2*(t - diff/d/2) + 1 - diff/d%2;
    }
    cout << ans << endl;
    return 0;
}