#include <bits/stdc++.h>
using namespace std;
#define int long long
#define in ({int x=0;int c=getchar(),n=0;for(;!isdigit(c);c=getchar()) n=(c=='-');for(;isdigit(c);c=getchar()) x=x*10+c-'0';n?-x:x;})
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int l,int r){return l+rng()%(r-l+1);}
#define fasty ios_base::sync_with_stdio(false),cin.tie(nullptr);
#define task "A"
#define forinc(a,b,c) for(int a=b,_c=c;a<=_c;++a)
#define fordec(a,b,c) for(int a=b,_c=c;a>=_c;--a)
#define forv(a,b) for(auto&a:b)
#define fi first
#define se second
#define pb push_back
#define ii pair<int,int>
#define mt make_tuple
#define all(a) a.begin(),a.end()
#define reset(f, x) memset(f, x, sizeof(f))
#define bit(x,i) ((x>>(i-1))&1)
#define on(x,i) (x|(1ll<<(i-1)))
#define off(x,i) (x&~(1<<(i-1)))
main(){
//freopen(task".inp","r",stdin);
//freopen(task".out","w",stdout);
int n=in,a=in,b=in,sz=a/__gcd(a,b+1)*b;
vector<ii> tmp;
forinc(i,1,n){
int l=in,r=in;
if(r-l+1>sz) return cout<<sz,0;
l=l%sz; r=r%sz;
if(l<=r) tmp.pb({l,r});
else tmp.pb({l,sz-1}),tmp.pb({0,r});
}
sort(all(tmp));
int ret=0;
forinc(i,0,tmp.size()-1){
int j=i,hold=tmp[i].se;
while(j<tmp.size() && tmp[j].fi<=hold){
hold=max(hold,tmp[j].se);
j++;
}
ret+=hold-tmp[i].fi+1;
i=j-1;
}
cout<<ret;
}
