#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define FOR(i, a, b) for (int i = a, _b = b; i <= _b; ++i)
#define FORD(i, a, b) for (int i = a, _b = b; i >= _b; --i)
#define FORLL(i, a, b) for (ll i = a, _b = b; i <= _b; ++i)
#define FORDLL(i, a, b) for (ll i = a, _b = b; i >= _b; --i)
#define all(x) x.begin(), x.end()
#define uni(x) sort(all(x)), x.erase(unique(all(x)), x.end())
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define dbg(...) debug(#__VA_ARGS__, __VA_ARGS__)
template<typename T>
void __print_one(const char *&s, const T &x)
{
while (*s == ' ') ++s;
const char *p = s;
int bal = 0;
while (*s)
{
if (*s == '(') ++bal;
else if (*s == ')') --bal;
else if (*s == ',' && bal == 0) break;
++s;
}
cerr.write(p, s - p) << " = " << x;
if (*s == ',')
{
++s;
cerr << " , ";
}
}
template<typename... Args>
void debug(const char *s, Args... args)
{
cerr << "[ ";
int dummy[] = { 0 , ( __print_one(s, args) , 0 )... };
(void)dummy;
cerr << " ]\n\n";
}
template<class X>
bool maximize(X &a, X b)
{
if (a < b)
{
a = b;
return true;
}
return false;
}
template<class X>
bool minimize(X &a, X b)
{
if (a > b)
{
a = b;
return true;
}
return false;
}
// --------------------------------------------------------------------------------------------
int n;
ll A, B;
vector<pll> segs;
// --------------------------------------------------------------------------------------------
pll get_time(ll x)
{
return pll((x + (x / B)) % A, x % B);
}
namespace sub1
{
bool approve()
{
ll sum = 0;
for (const auto &p : segs)
{
sum += p.se - p.fi + 1;
if (sum > ll(1e6)) return false;
}
return true;
}
void solve()
{
vector<pll> vecres;
for (const auto &e : segs)
{
FORLL(i, e.fi, e.se)
{
vecres.push_back(get_time(i));
}
}
uni(vecres);
cout << (int)vecres.size();
}
}
namespace sub2
{
ll gcd(ll a, ll b)
{
if (b == 0) return a;
return gcd(b, a % b);
}
void solve()
{
ll lap = A / gcd(A, (B + 1) % A);
if ((B + 1) <= ll(1e18) / lap) lap *= B;
else lap = ll(1e18) + 1;
if (lap == 0) lap = A + 1;
ll len = segs[0].se - segs[0].fi + 1;
ll res = min(len, lap);
cout << res;
dbg(len == res);
}
}
namespace AC
{
ll gcd(ll a, ll b)
{
if (b == 0) return a;
return gcd(b, a % b);
}
void solve()
{
ll lap = A / gcd(A, (B + 1) % A);
if (B <= ll(1e18) / lap) lap *= B;
else lap = ll(1e18) + 1;
if (lap == 0) lap = A + 1;
vector<pll> vec;
for (const auto &p : segs)
{
ll len = p.se - p.fi + 1;
if (len >= lap) return void(cout << lap);
ll sta = p.fi % lap, ed = p.se % lap;
if (sta <= ed) vec.push_back({sta, ed});
else
{
vec.push_back({0, ed});
vec.push_back({sta, lap - 1});
}
}
vector<pll> vecres;
ll res = 0;
sort(all(vec));
pll cur = vec[0];
FOR(i, 1, int(vec.size()) - 1)
{
auto &p = vec[i];
if (p.fi > cur.se)
{
res += cur.se - cur.fi + 1;
cur = p;
}
else if (p.se > cur.se)
{
cur.se = p.se;
}
}
res += cur.se - cur.fi + 1;
cout << res;
}
}
void solve()
{
cin >> n >> A >> B;
FOR(i, 1, n)
{
ll l, r; cin >> l >> r;
segs.push_back({l, r});
}
// if (sub1 :: approve()) return sub1 :: solve(), void();
// sub2 :: solve();
AC :: solve();
}
signed main()
{
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define TASK "TEST"
if (fopen(TASK".INP", "r"))
{
freopen(TASK".INP", "r", stdin);
freopen(TASK".OUT", "w", stdout);
}
solve();
return 0;
}
