#include <bits/stdc++.h>
using namespace std;
#define ll long long
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define usecppio ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define all(x) ((x).begin()),((x).end())
#define int __int128
using pii = pair <int, int>;
#define INF 0x7f7f7f7f7f7f7f7f
const bool debug = false;
std::ostream&operator<<( std::ostream& dest, __int128_t value )
{
std::ostream::sentry s( dest );
if ( s ) {
__uint128_t tmp = value < 0 ? -value : value;
char buffer[ 128 ];
char* d = std::end( buffer );
do
{
-- d;
*d = "0123456789"[ tmp % 10 ];
tmp /= 10;
} while ( tmp != 0 );
if ( value < 0 ) {
-- d;
*d = '-';
}
int len = std::end( buffer ) - d;
if ( dest.rdbuf()->sputn( d, len ) != len ) {
dest.setstate( std::ios_base::badbit );
}
}
return dest;
}
int n, a, b;
int period;
vector <pii> v;
vector <pii> range;
int32_t main()
{
usecppio
ll _n, _a, _b;
cin >> _n >> _a >> _b;
n = _n, a = _a, b = _b;
period = (a/(__gcd(a, b+1)))*b;
for (int i = 0; i<n; i++)
{
ll l, r; cin >> l >> r;
v.push_back({l, r});
if (r - l + 1 >= period)
{
cout << period << '\n';
return 0;
}
if (l%period <= r%period)
{
range.push_back({l%period, r%period});
}
else
{
range.push_back({0, r%period});
range.push_back({l%period, period-1});
}
}
sort(all(range));
int start = range[0].first;
int end = range[0].second;
int ans = 0;
for (int i = 1; i<range.size(); i++)
{
if (range[i].first > end)
{
ans += end-start+1;
start = range[i].first;
end = range[i].second;
}
else
end = max(end, range[i].second);
}
ans += end-start+1;
cout << ans << '\n';
}
