#include <bits/stdc++.h>
#include <numeric>
#define ll long long
#define ld long double
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pdd pair<double, double>
#define vi vector<int>
#define vl vector<ll>
#define ALL(x) x.begin(), x.end()
#define SZ(x) (int)x.size()
#define CASE int t;cin>>t;for(int ca=1;ca<=t;ca++)
#define IOS ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
const int MAX = 1 << 20, MOD = 1e9 + 7;
ll l[MAX], r[MAX];
void solve(){
ll n, a, b;
cin >> n >> a >> b;
for(int i = 1;i <= n;i++){
cin >> l[i] >> r[i];
}
ll g = __gcd(a, b + 1);
ll mod;
if((__int128_t)a * b / g >= 2e18)
mod = 2e18;
else
mod = a * b / g;
map<ll, int> mp;
for(int i = 1;i <= n;i++){
if(r[i] - l[i] + 1 >= mod){
cout << mod << '\n';
return;
}
l[i] %= mod;
r[i] %= mod;
if(l[i] <= r[i]){
mp[l[i]]++;
mp[r[i] + 1]--;
}else{
mp[0]++;
mp[r[i] + 1]--;
mp[l[i]]++;
mp[mod]--;
}
}
ll lt = 0, now = 0, ans = 0;
for(auto i : mp){
if(now > 0)
ans += i.F - lt;
now += i.S;
lt = i.F;
}
cout << ans << '\n';
}
int main(){
IOS
solve();
return 0;
}
