#include<bits/stdc++.h>
#define x first
#define y second
#define pb push_back
#define eb emplace_back
#define all(a) (a).begin(),(a).end()
#define SZ(a) (int)(a).size()
#define FOR(i, a, b) for(int i=(a); i<=(b); ++i)
#define ROF(i, a, b) for(int i=(a); i>=(b); --i)
#define make_unique(a) sort(all((a))), (a).resize(unique(all((a)))-(a).begin())
using namespace std;
typedef pair<int,int> PII;
typedef long long LL;
typedef double DD;
typedef long double LD;
typedef pair<LL,LL> PLL;
typedef pair<DD,DD> PDD;
typedef vector<int> VI;
typedef vector<LL> VL;
const int N = 1000005;
int n;
LL A, B;
set<PLL> keep;
set<PLL>::iterator it, it2;
void solve(){
scanf("%d %lld %lld",&n,&A,&B);
LL loop = A/__gcd(A,B+1);
if(loop > 1e18/B){
loop = 1e18+2;
}else loop *= B;
//printf("loop is %lld\n",loop);
int ch = 0;
LL ans = 0;
auto find = [&](LL a){
return keep.lower_bound(PLL(a,0));
};
auto add = [&](LL l, LL r){
//printf("adding (%lld, %lld)\n",l,r);
it = find(l+1);
if(it != keep.begin()) --it;
for(; it != keep.end();){
PLL e = *it;
it2 = it;
++it;
if(e.x > r+1) break;
if(e.y < l-1) continue;
l = min(l, e.x); r = max(r, e.y);
keep.erase(it2);
}
keep.insert(PLL(l,r));
};
FOR(i, 1, n){
LL l, r;
scanf("%lld %lld",&l,&r);
if(r-l+1 >= loop){
ch = 1; ans = loop;
}
// there is a function called 'prev'
l %= loop;
r %= loop;
if(l > r) add(0,r), add(l,loop-1);
else add(l,r);
//printf("keep : ");
//for(PLL e : keep) printf("[%lld, %lld] ",e.x,e.y);
//puts("");
}
if(ch){ printf("%lld",ans); return ; }
for(PLL e : keep) ans += e.y-e.x+1;
printf("%lld",ans);
}
int main(){
solve();
return 0;
}
/*
*
*
*
*
*
*
*
*
*
*
*/
