#include "bits/stdc++.h"
#define pb push_back
#define int long long
using namespace std;
const int inf = 3e18;
const int N = 1e6;
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int n, a, b;
cin>>n>>a>>b;
vector<int> l(n), r(n);
for(int i = 0; i < n; i++){
cin>>l[i]>>r[i];
l[i]--, r[i]--;
}
bool big = 0;
int gc = gcd(a, b+1);
big |= (a > inf / gc / b);
big |= (b > inf / gc / a);
big |= (gc > inf / a / b);
if(big){
int tot = 0;
for(int i = 0; i < n; i++){
int len = r[i] - l[i] + 1;
tot += len;
}
cout<<tot<<endl;
return 0;
}
int per = a / gc * b;
bool all = 0;
vector<pair<int, int> > upd;
set<int> ste;
int add0 = 0;
for(int i = 0; i < n; i++){
int df = (r[i] / per) - (l[i] / per);
int lmod = l[i] % per;
int rmod = r[i] % per;
ste.insert(lmod);
ste.insert(rmod+1);
if(r[i] - l[i] + 1 >= per) all = 1;
else if(df == 1){
add0++;
}
upd.pb({lmod, rmod+1});
}
ste.insert(0);
ste.insert(per);
vector<int> vec;
for(auto itr: ste){
vec.pb(itr);
}
vector<int> add(ste.size());
add[0] += add0;
for(auto itr: upd){
auto l = lower_bound(vec.begin(), vec.end(), itr.first) - vec.begin();
auto r = lower_bound(vec.begin(), vec.end(), itr.second) - vec.begin();
add[l]++;
add[r]--;
}
if(all){
cout<<per<<endl;
}
else{
int ans = 0, now = 0;
for(int i = 0; i < vec.size()-1; i++){
now += add[i];
if(now > 0){
ans += vec[i+1] - vec[i];
}
}
cout<<ans<<endl;
}
return 0;
}
