/// Just for others, not for me :( 9 days and counting
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> pii;
LL A, B;
int main()
{
//freopen("1.in", "r", stdin);
int T;
cin >> T >> A >> B;
LL d = __gcd(A, B + 1);
LL K = A / d;
K *= B;
vector<pii> itvs;
for(int i = 1; i <= T; i++)
{
LL st, dr;
cin >> st >> dr;
if(dr - st + 1 >= K)
{
cout << K << '\n';
exit(0);
}
st %= K, dr %= K;
if(st <= dr)
itvs.push_back({st, dr});
else
{
itvs.push_back({st, K - 1});
itvs.push_back({0, dr});
}
}
sort(itvs.begin(), itvs.end(),
[](pii a, pii b)
{
if(a.second == b.second) return a.first < b.first;
return a.second < b.second;
});
LL ans = 0;
while(!itvs.empty())
{
pii itv = itvs.back();
itvs.pop_back();
while(!itvs.empty())
{
if(itvs.back().second >= itv.first)
{
pii itv2 = itvs.back();
itvs.pop_back();
itv.first = min(itv.first, itv2.first);
}
else
break;
}
ans += itv.second - itv.first + 1;
}
cout << ans << '\n';
}
