#include <bits/stdc++.h>
using namespace std;
typedef long long i64;
typedef pair<i64, i64> pii;
#define ff first
#define ss second
#define MP make_pair
struct tree {
i64 tl, tr, sum;
tree *lc, *rc;
bool lazy;
tree(i64 l, i64 r) {
tl = l;
tr = r;
sum = 0;
lazy = 0;
lc = NULL;
rc = NULL;
}
void upt(i64 l, i64 r) {
if(lazy) return;
if(tl == l && r == tr) {
sum = r - l + 1;
lazy = 1;
return;
}
i64 tm = (tl + tr) / 2;
if(lc == NULL) lc = new tree(tl, tm);
if(rc == NULL) rc = new tree(tm + 1, tr);
if(r <= tm) lc-> upt(l, r);
else if(tm < l) rc-> upt(l, r);
else {
lc-> upt(l, tm);
rc-> upt(tm + 1, r);
}
sum = lc-> sum + rc-> sum;
if(lc-> lazy && rc-> lazy)
lazy = 1;
}
};
i64 gcd(i64 a, i64 b) {
if(a == 0) return b;
if(b == 0) return a;
return gcd(b % a, a);
}
int main() {
int n, gay = 0;
i64 A, B;
cin >> n >> A >> B;
i64 T = A / gcd(A, B + 1) * B;
// cout << T << endl;
tree *root = new tree(0, T - 1);
vector<pii> v;
for(int i = 0; i < n; i++) {
i64 l, r;
cin >> l >> r;
l %= T;
r %= T;
// cout << l << ' ' << r << endl;
if(gay) continue;
if(r - l + 1 >= T) {
gay = 1;
continue;
}
if(l <= r) {
// cout << " > " << l << ' ' << r << endl;
// root-> upt(l, r);
v.push_back(MP(l, r));
}
else {
// cout << " > " << l << ' ' << T - 1 << endl;
// cout << " > " << 0 << ' ' << r << endl;
// root-> upt(l, T - 1);
// root-> upt(0, r);
v.push_back(MP(l, T - 1));
v.push_back(MP(0, r));
}
}
if(gay) {
cout << T << endl;
return 0;
}
sort(v.begin(), v.end());
i64 ans = 0;
i64 l = 0, r = 0;
for(pii p : v) {
if(r < p.ff) {
// cout << l << ' ' << r << endl;
ans += (r - l + 1);
l = p.ff;
}
r = p.ss;
}
// cout << l << ' ' << r << endl;
ans += (r - l + 1);
cout << ans << endl;
return 0;
}
