#include <cmath>
#include <functional>
#include <fstream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <map>
#include <list>
#include <time.h>
#include <math.h>
#include <random>
#include <deque>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <cassert>
#include <bitset>
#include <sstream>
#include <chrono>
#include <cstring>
#include <numeric>
#include <cstdint>
#include <limits>
#include <numeric>
#include <iostream>
using namespace std;
#define int long long
pair<int, int> get(int t, int a, int b)
{
int x = (t + t / b) % a;
int y = t % b;
return { x, y };
}
bool same_dumb(int t1, int t2, int a, int b)
{
return get(t1, a, b) == get(t2, a, b);
}
int gcd(int a, int b)
{
if (b == 0) return a;
return gcd(b, a % b);
}
bool same_smart(int t1, int t2, int a, int b)
{
a /= gcd(a, b + 1);
a *= b;
return t1 % a == t2 % a;
}
const int lim = 20;
void print(vector<int> v)
{
cout << " ---> ";
for (auto& x : v)
{
cout << x << " ";
}
cout << "\n";
}
void solve()
{
int n, mod;
cin >> n;
{
int a, b;
cin >> a >> b;
a /= gcd(a, b + 1);
a *= b;
mod = a;
}
set<int> s;
vector<pair<int, int>> segs(n);
for (auto& it : segs)
{
cin >> it.first >> it.second;
for (int j = it.first; j <= it.second; j++) s.insert(j % mod);
}
cout << (int)s.size() << "\n";
exit(0);
}
signed main()
{
#ifdef ONPC
FILE* stream;
freopen_s(&stream, "input.txt", "r", stdin);
#else
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#endif
solve();
int cnt = 0;
for (int a = 2; a <= lim; a++)
{
for (int b = 1; b <= lim; b++)
{
for (int t = 0; t <= 2 * a * b; t++)
{
for (int t2 = 0; t2 <= 2 * a * b; t2++)
{
bool s1 = same_dumb(t, t2, a, b);
bool s2 = same_smart(t, t2, a, b);
if (s1 != s2)
{
cout << "WA!\n";
return 0;
}
}
}
cout << "done " << a << " " << b << "\n";
}
}
cout << "Ac!\n";
return 0;
}
