#include<bits/stdc++.h>
#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ff first
#define ss second
#define vi vector<int>
#define vl vector<ll>
#define vii vector<pii>
#define vll vector<pll>
#define FOR(i,N) for(i=0;i<(N);++i)
#define FORe(i,N) for(i=1;i<=(N);++i)
#define FORr(i,a,b) for(i=(a);i<(b);++i)
#define FORrev(i,N) for(i=(N);i>=0;--i)
#define F0R(i,N) for(int i=0;i<(N);++i)
#define F0Re(i,N) for(int i=1;i<=(N);++i)
#define F0Rr(i,a,b) for(ll i=(a);i<(b);++i)
#define F0Rrev(i,N) for(int i=(N);i>=0;--i)
#define all(v) (v).begin(),(v).end()
#define dbgLine cerr<<" LINE : "<<__LINE__<<"\n"
#define ldd long double
using namespace std;
const int Alp = 26;
const int __PRECISION = 9;
const int inf = 1e9 + 8;
const ldd PI = acos(-1);
const ldd EPS = 1e-7;
const ll MOD = 1e9 + 7;
const ll MAXN = 2e5 + 5;
const ll ROOTN = 320;
const ll LOGN = 18;
const ll INF = 1e18 + 1022;
ll n, A, B, l, r, sm, mxDiff, T;
vll V, ranges;
ll gcd(ll a, ll b)
{
if(a > b)
swap(a, b);
if(b % a == 0)
return a;
return gcd(b%a, a);
}
inline void check_period()
{
ll tmp = gcd(A, B+1);
if(log2(A*1.0) + log(B*1.0) - log(1.0 * tmp) > 59.99)
{
cout<<sm<<'\n';
exit(0);
}
T = B * (A / tmp);
if(mxDiff >= T)
{
cout<<T<<'\n';
exit(0);
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
sm = mxDiff = 0;
cin>>n>>A>>B;
F0R(i, n)
{
cin>>l>>r;
sm += r - l + 1;
mxDiff = max(mxDiff, r-l+1);
ranges.pb(mp(l, r));
}
check_period();
sm = 0;
F0R(i, n)
{
l = ranges[i].ff % T, r = ranges[i].ss % T;
V.pb(mp(l, 0));
V.pb(mp(r, 1));
if(l > r)
V.pb(mp(T-1, 1)), V.pb(mp(0, 0));
}
// cerr<<"period = "<<T<<'\n';
sort(all(V));
// for(pll x : V)
// cout<<"("<<x.ff<<','<<x.ss<<")\n";
ll lst = -1, act = 0;
for(pll pp : V)
{
if(act == 0 and pp.ss == 0)
++sm;
if(act > 0)
sm += pp.ff - lst;
if(pp.ss == 0)
++act;
else if(pp.ss == 1)
--act;
lst = pp.ff;
}
cout<<sm<<'\n';
return 0;
}
