#include <bits/stdc++.h>
using namespace std;
#define v vector
#define int unsigned long long
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define mk make_pair
#define pii pair<int, int>
#define ff first
#define ss second
#define inp_v(vec) for (auto &i : vec) cin >> i;
#define prt_v(vec) for (auto i : vec) cout << i << endl;
#define MS(x) memset(x, 0, sizeof(x))
#define gcd(a,b) __gcd(a, b);
#define lcm(a,b) (a*(b/gcd(a,b)))
#define lb lower_bound
#define ub upper_bound
bool chmin(int &a, int b){return b<a?a=b, true:false;}
bool chmax(int &a, int b){return b>a?a=b, true:false;}
// bool comp(const pair<int, int>&a, const pair<int int>&b){
// return a.second<b.second;
// }
signed main(){
ios_base::sync_with_stdio(false); cin.tie(0);
int N, a, b;cin>>N>>a>>b;
double cycles=a/(__gcd(a, b+1))*b;
int cycle=(int)cycles;
vector<pair<int, int>>segment;
vector<pair<int, int>>seg;
bool flag=false;
for(int i=0;i<N;i++){
int x, y;cin>>x>>y;
if(y-x+1>=cycle){
flag=true;
}
if(y>=cycle){
// cout<<i<<" "<<x<<" "<<cycle<<" "<<y%cycle<<endl;
if(x>=cycle){
if(y/cycle>x/cycle){
segment.push_back({x%cycle, cycle-1});
segment.push_back({0, y%cycle});
}
else segment.push_back({x%cycle, y%cycle});
// segment.push_back({0, y%cycle});
}
else{
segment.push_back({x, cycle-1});
segment.push_back({0, y%cycle});
}
}
else{
segment.push_back({x, y});
}
}
sort(segment.begin(), segment.end());
int curl=segment[0].first, curr=segment[1].second;
int ans=curr-curl+1;
// cout<<cycle<<endl;
for(int i=1;i<segment.size();i++){
// cout<<segment[i].first<<" "<<segment[i].second<<endl;
if(curr>=segment[i].second){
continue;
}
else{
curl=max(curr+1, segment[i].first);
curr=segment[i].second;
ans+=curr-curl+1;
}
}
if(flag)cout<<cycle<<endl;
else cout<<ans<<endl;
return 0;
}
