#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
#define endl '\n'
#define pi pair<long long, long long>
const long long inf = 2000000000000000000;
const int maxn = 2000001;
long long n, m, a, b;
pi p[maxn];
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> a >> b;
m = __gcd(b + 1, a) % a;
m += a * (m == 0);
m = min(inf / b, a / m) * b;
for(int i = 0; i < n; i++){
cin >> p[i].first >> p[i].second;
if(p[i].second - p[i].first >= m) p[i] = {0, m - 1};
p[i].first %= m, p[i].second %= m;
if(p[i].second < p[i].first){
p[i + 1] = {p[i].first, m - 1};
p[i].first = 0;
i++, n++;
}
}
p[n] = {m, m};
sort(p, p + n);
long long ret = 0;
for(long long i = 0, j = p[0].second, k = p[0].first; i < n; i++){
j = max(j, p[i].second);
if(j < p[i + 1].first){
ret += j - k + 1;
k = p[i + 1].first;
}
}
cout << ret << endl;
return 0;
}
