#include <bits/stdc++.h>
using namespace std;
using ll = long long;
class SparseSegtree {
private:
struct Node {
int freq = 0;
int lazy = 0;
int left = -1;
int right = -1;
};
vector<Node> tree;
const int n;
int timer = 0;
int comb(int a, int b) { return a + b; }
void apply(int cur, int len, int val) {
if (val == 1) {
tree[cur].lazy = val;
tree[cur].freq = len * val;
}
}
void push_down(int cur, int l, int r) {
if (tree[cur].left == -1) {
tree[cur].left = ++timer;
tree.push_back(Node());
}
if (tree[cur].right == -1) {
tree[cur].right = ++timer;
tree.push_back(Node());
}
int m = (l + r) / 2;
apply(tree[cur].left, m - l + 1, tree[cur].lazy);
apply(tree[cur].right, r - m, tree[cur].lazy);
tree[cur].lazy = 0;
}
void range_set(int cur, int l, int r, int ql, int qr, int val) {
if (qr < l || ql > r) { return; }
if (ql <= l && r <= qr) {
apply(cur, r - l + 1, val);
} else {
push_down(cur, l, r);
int m = (l + r) / 2;
range_set(tree[cur].left, l, m, ql, qr, val);
range_set(tree[cur].right, m + 1, r, ql, qr, val);
tree[cur].freq =
comb(tree[tree[cur].left].freq, tree[tree[cur].right].freq);
}
}
int range_sum(int cur, int l, int r, int ql, int qr) {
if (qr < l || ql > r) { return 0; }
if (ql <= l && r <= qr) { return tree[cur].freq; }
push_down(cur, l, r);
int m = (l + r) / 2;
return comb(range_sum(tree[cur].left, l, m, ql, qr),
range_sum(tree[cur].right, m + 1, r, ql, qr));
}
public:
SparseSegtree(int n, int q = 0) : n(n) {
if (q > 0) { tree.reserve(2 * q * __lg(n)); }
tree.push_back(Node());
}
void range_set(int ql, int qr, int val) { range_set(0, 0, n - 1, ql, qr, val); }
int range_sum(int ql, int qr) { return range_sum(0, 0, n - 1, ql, qr); }
};
int main() {
ll n, a, b; cin >> n >> a >> b;
ll bruda = ((b%a) == a-1) ? a : -1;
if (bruda == -1) {
if (a > (ll)1e18/b) {
bruda = (ll)1e18+1;
} else {
bruda = a*b;
}
}
// cout << k << "\n";
set<pair<ll, ll>> st;
SparseSegtree seg(bruda, 2*n);
for (int i = 0; i < n; i++) {
ll a1, b1; cin >> a1 >> b1;
a1 %= bruda;
b1 %= bruda;
if (a1 > b1) {
seg.range_set(a1, bruda-1, 1);
seg.range_set(0, b1, 1);
} else {
seg.range_set(a1, b1, 1);
}
}
cout << seg.range_sum(0, bruda);
}
