#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define FOR(i,a,b) for (auto i = (a); i <= (b); ++i)
#define NFOR(i,a,b) for(auto i = (a); i >= (b); --i)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
#define mp(i,a) make_pair(i,a)
#define pb(a) push_back(a)
#define bit(x,b) (x&(1LL<<b))
typedef long long int lli;
typedef pair <lli,lli> ii;
typedef pair <lli,ii> iii;
typedef vector <lli> vi;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
lli test=1;
for(;test>0;--test)
{
lli n,a,b,g,p,f,s,cl,cr,ans=0,ch=1;
cin>>n>>a>>b;
g=__gcd(a,b+1);
g=a/g;
if(1.0*g*b>1000000000000000000)
p=1000000000500000000;
else
p=g*b;
vector<ii> v;
for(lli i=0;i<n;++i)
{
cin>>f>>s;
if(f-s+1>=p)
{
ch=0;
}
f%=p;
s%=p;
if(f<=s)
v.pb(mp(f,s));
else
{
v.pb(mp(0,s));
v.pb(mp(f,p-1));
}
}
if(ch==0)
{
cout<<p<<endl;
exit(0);
}
sort(all(v));
v.pb(mp(p,p));
cl=0;
cr=-1;
ans=0;
for(lli i=0;i<v.size();++i)
{
if(v[i].F<=cr&&v[i].S>=cr)
{
cr=v[i].S;
}
else
{
ans+=cr-cl+1;
cl=v[i].F;
cr=v[i].S;
}
}
cout<<ans<<endl;
}
return(0);
}
