#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define pii pair<long long int,long long int>
#define vi vector<long long int >
#define vvi vector<vector< long long int>>
#define MP make_pair
#define PB push_back
#define pb pop_back
#define PF push_front
#define pf pop_front
#define MOD 1000000007
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll n,a,b;
vector<pii> vec;
cin>>n>>a>>b;
for(ll i=0;i<n;i++)
{
ll x,y;
cin>>x>>y;
vec.PB(MP(x,y));
}
// solve equation t2 = x*fac+t1
ll fac = a/__gcd(a,b+1);
fac*=b;
if(fac<=0)
fac=1e18+1;
ll ans=0;
vector<pii> ve;
for(ll i=0;i<n;i++)
{
ll x=vec[i].first,y=vec[i].second;
if(y-x+1>=fac)
{
ans=fac;
break;
}
if((x%fac)<=(y%fac))
{
ve.PB(MP(x%fac,y%fac));
}
else
{
ve.PB(MP(x%fac,fac-1));
ve.PB(MP(0,y%fac));
}
}
if(ans==0)
{
sort(ve.begin(),ve.end());
ll k=ve.size();
for(ll i=0;i<k;i++)
{
ll x=ve[i].first,y=ve[i].second;
ll j=i+1;
//cout<<x<<" "<<y<<endl;
while(j<k && ve[j].first<=(y+1))
{
y=max(ve[j].second,y);
//cout<<x<<" "<<y<<endl;
j++;
}
ans+= (y-x+1);
i=j-1;
}
}
cout<<ans<<"\n";
return 0;
}
