#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e6 + 11;
ll n, a, b, c, res, sz = 1;
ll l[N], r[N], was[N], t[20 * N];
int lv[30 * N], rv[30 * N], lzy[30 * N];
__int128 val;
void push(ll v, ll l, ll r){
if(lzy[v] == 0) return;
if(l != r){
if(!lv[v]) lv[v] = ++sz;
if(!rv[v]) rv[v] = ++sz;
lzy[lv[v]] = lzy[rv[v]] = 1;
}
t[v] = (r - l + 1);
}
void upd(ll tl, ll tr, ll x, ll v = 1, ll l = 0, ll r = c - 1){
push(v, l, r);
if(r < tl || tr < l) return;
if(tl <= l && r <= tr){
lzy[v] = 1, push(v, l, r);
return;
}
ll md = (l + r) / 2;
if(!lv[v]) lv[v] = ++sz;
if(!rv[v]) rv[v] = ++sz;
upd(tl, tr, x, lv[v], l, md);
upd(tl, tr, x, rv[v], md + 1, r);
t[v] = t[lv[v]] + t[rv[v]];
}
void solve(){
cin >> n >> a >> b;
for(ll i = 1; i <= n; i++) cin >> l[i] >> r[i];
val = a / __gcd(a, b + 1), val *= b;
if(val > 1e18){
for(ll i = 1; i <= n; i++) res += r[i] - l[i] + 1;
cout << res;
return;
}
c = val;
for(ll i = 1; i <= n; i++){
if(r[i] - l[i] + 1 >= c){
cout << c << '\n';
return;
}
l[i] %= c, r[i] %= c;
if(l[i] <= r[i]) upd(l[i], r[i], 1);
else upd(l[i], c - 1, 1), upd(0, r[i], 1);
}
cout << t[1];
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while(tt--) solve();
}
