#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=1e6+10, inf=2e18;
int n, a, b;
int l[N], r[N];
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> a >> b;
for (int i=1; i<=n; ++i) cin >> l[i] >> r[i];
int mod=a/__gcd(b+1, a);
if (mod>inf/b){
int ans=0;
for (int i=1; i<=n; ++i) ans+=r[i]-l[i]+1;
cout << ans << '\n';
return 0;
}
mod*=b;
vector<pair<int, int>> v;
for (int i=1; i<=n; ++i){
if (r[i]-l[i]+1>=mod){
cout << mod << '\n';
return 0;
}
l[i]%=mod; r[i]%=mod;
if (l[i]>r[i]){
v.emplace_back(l[i], mod-1);
v.emplace_back(0, r[i]);
}else{
v.emplace_back(l[i], r[i]);
}
}
sort(v.begin(), v.end());
int ans=0;
int ll=0, rr=-1;
for (auto &i:v){
if (rr+1>=i.first) rr=max(rr, i.second);
else{
ans+=rr-ll+1;
ll=i.first, rr=i.second;
}
}
cout << ans+rr-ll+1 << '\n';
return 0;
}
