#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<set>
#include<queue>
#include<stack>
#include<bitset>
#include<functional>
#include<map>
#include<iomanip>
#include<limits>
#include<unordered_set> 
#include<cmath>
using namespace std;
//long long p = 998244353;
long long p = 1000000007;
#define int long long
#define vel vector<long long>
#define vvel vector<vel>
#define rep(i,n) for(int i=0;i<n;i++)
#define sor(v) sort(v.begin(),v.end())
#define mmax(a,b) a=max(a,b)
#define mmin(a,b) a=min(a,b)
#define mkp make_pair
#define pin pair<int,int>
#define qin pair<pin,int>
#define V vector
#define Endl endl
#define veb vector<bool>
#define fcout cout << fixed << setprecision(15)
#define rev(s) reverse(s.begin(),s.end())
#define lower(h,val) lower_bound(h.begin(),h.end(),val)-h.begin()
#define upper(h,val) upper_bound(h.begin(),h.end(),val)-h.begin()
int max_kai = 150000;
vel kai(max_kai, 1);
vel inv_kai;
int rui(int a, int n, int mod) {
    if (n == 0) { return 1 % mod; }
    int x = rui(a, n / 2, mod);
    x *= x; x %= mod;
    if (n % 2 == 1) { x *= a; x %= mod; }
    return x;
}
vel pa;
int root(int x) {
    if (pa[x] == -1) { return x; }
    int ans = root(pa[x]); pa[x] = ans;
    return ans;
}
void marge(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) { pa[x] = y; }
}
int gcd(int x, int y) {
    if (x < y) { return gcd(y, x); }
    if (y == 0) { return x; }
    return gcd(y, x % y);
}
long long modinv(long long a, long long m) {
    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m;
    if (u < 0) u += m;
    return u;
}
vel uni(vel &x) {
    if (x.size() == 0) { return x; }
    sor(x);
    int n = x.size();
    vel ans(1, x[0]);
    for (int j = 1; j < n; j++) {
        if (x[j - 1] != x[j]) { ans.push_back(x[j]); }
    }
    x = ans;
    return x;
}
signed main() {
    int x, d, n; cin >> n >> x >> d;
    if (d == 0) {
        if (x == 0) { cout << 1 << endl; return 0; }
        cin >> n; cout << n+1 << endl;
        return 0;
    }
    if (d < 0) {
        x += d * (n - 1);
        d *= -1;
    }
    int g1 = gcd(abs(x), d);
    x /= g1; d /= g1;
    int ans = 0;
    rep(i, min(n+1, d)) {
        vel st;
        vel to;
        vel all;
        for (int j = 0; j*d+i <= n; j++) {
            int count = j * d + i;
            int qc = count - 1;
            int minj = (count*qc) / 2;
            int maxj = (n - 1) * count - minj;
            minj += j * x;
            maxj += j * x;
            maxj++;
            st.push_back(minj); all.push_back(minj);
            to.push_back(maxj); all.push_back(maxj);
        }
        int m = st.size();
        uni(all);
        int sz = all.size();
        vel imos(sz, 0);
        rep(j, m) {
            int s1 = lower_bound(all.begin(), all.end(), st[j]) - all.begin();
            int t1 = lower_bound(all.begin(), all.end(), to[j]) - all.begin();
            imos[s1]++; imos[t1]--;
        }
        rep(j, sz-1) {
            if (j != 0) { imos[j] += imos[j - 1]; }
            if (imos[j] > 0) { ans += all[j + 1] - all[j]; }
        }
    }
    cout << ans << endl;
    return 0;
}


Measured memory_bytes: 19420