// FUCKED UP FUCKED UP FUCKED UP FUCKED UP FUCKED UP
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O2,no-stack-protector,unroll-loops,fast-math")
#define F first
#define S second
#define pb push_back
#define SZ(x) (ll)(x.size())
#define all(x) x.begin(),x.end()
#define MP make_pair
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll maxn=1e6+10, maxm=1e6+10, lg=21, mod=998244353, inf=1e18+10;
ll n,A,B,m;
map<ll,ll> ss;
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
cin>>n>>A>>B;
ll g=__gcd(A,B+1);
m=A/g;
if(B>inf/m+10) m=inf;
else m*=B;
while(n--){
ll l,r; cin>>l>>r; r++;
if(r-l>=m) return cout<<m,0;
l%=m, r%=m;
ss[l]++, ss[r]--;
if(l>=r) ss[0]++, ss[m]--;
}
ll ans=0,ls=0,ps=0;
for(auto x:ss){
if(ps) ans+=x.F-ls;
ls=x.F, ps+=x.S;
}
cout<<ans;
return 0;
}
