#include<bits/stdc++.h>
#define st first
#define nd second
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define eb emplace_back
#define pp pop_back
#define mp make_pair
using namespace std;
using pii = pair<int, int>;
using ll = long long;
using vi = vector<int>;
using vii = vector<pii>;
void debug(){cerr<<"\n";}
template<typename H, typename... T>
void debug(H h, T... t){
cerr<<h;
if(sizeof...(t)){
cerr<<", ";
}
debug(t...);
}
#define deb(x...) cerr<<#x<<" = ";debug(x);
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
int main(){
int n;
ll a, b;
cin>>n>>a>>b;
if(b>=ll(1e18)/(a/gcd(a, b+1))){
ll s=0;
for(int i=0; i<n; i++){
ll l, r;
cin>>l>>r;
s+=r-l+1;
}
cout<<s;
return 0;
}
ll t=b*(a/__gcd(a, b+1));
vector<ll> V;
for(int i=0; i<n; i++){
ll l, r;
cin>>l>>r;
for(ll j=l; j<=r; j++){
V.pb(j%t);
}
}
sort(all(V));
V.resize(unique(all(V))-V.begin());
cout<<V.size();
}
