#include <bits/stdc++.h>
#define int long long
using namespace std;
int gcd(int a, int b) {
a = abs(a);
b = abs(b);
if(a < b) swap(a, b);
while(b) {
a %= b;
swap(a, b);
}
return a;
}
vector<int> B;
int getidx(int n) {
return lower_bound(B.begin(),B.end(),n) - B.begin();
}
struct SegTree {
vector<int> seg;
int MAX;
SegTree(int N) {
int i;
for(i=2;i<2*N;i*=2) {}
seg.resize(i);
MAX = i;
}
int sum(int s, int e, int n, int ns, int ne) {
if(e<=ns||ne<=s) return 0;
if(s<=ns&&ne<=e) return seg[n];
int mid = ns + ne >> 1;
return sum(s, e, 2*n, ns, mid) + sum(s, e, 2*n+1, mid, ne);
}
void update(int n) {
n += MAX/2;
n /= 2;
while(n) {
seg[n] = seg[2*n] + seg[2*n+1];
n /= 2;
}
}
void Plus(int n) {
seg[n+MAX/2]++;
update(n);
}
void Minus(int n) {
seg[n+MAX/2]--;
update(n);
}
int sum(int s, int e) {
return sum(s, e, 1, 0, MAX/2);
}
};
int L[1000005];
int R[1000005];
main() {
cin.sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int N, a, b;
cin >> N >> a >> b;
int d = gcd(a, b + 1);
int c = a / d;
assert(a % d == 0);
__int128_t k2 = b * c;
int k;
if(k2 > 1e18 + 5) k = 1e18 + 5;
else k = k2;
assert(k < 1e18 + 10);
bool isAll = false;
int i;
B.push_back(0);
B.push_back(k);
for(i=0;i<N;i++) {
cin >> L[i] >> R[i];
if(R[i] - L[i] >= k-1) isAll = true;
L[i] %= k;
R[i] %= k;
R[i]++;
B.push_back(L[i]);
B.push_back(R[i]);
}
sort(B.begin(),B.end());
B.erase(unique(B.begin(),B.end()),B.end());
SegTree tree(B.size() + 10);
for(i=0;i<N;i++) {
int l = getidx(L[i]);
int r = getidx(R[i]);
if(l < r) {
tree.Plus(l);
tree.Minus(r);
}
else {
tree.Plus(0);
tree.Minus(r);
tree.Plus(l);
tree.Minus(B.size());
}
}
int cnt = 0;
for(i=0;i<B.size()-1;i++) {
if(tree.sum(0,i+1)!=0) {
cnt += B[i+1]-B[i];
}
}
if(isAll) cnt = k;
cout << cnt;
}
