#include "bits/stdc++.h"
#define pb push_back
#define int long long
using namespace std;
const int inf = 2e18;
const int mod = 998244353;
const int N = 2e6 + 5;
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int n, a, b;
cin>>n>>a>>b;
vector<int> l(n), r(n);
for(int i = 0; i < n; i++){
cin>>l[i]>>r[i];
l[i]--, r[i]--;
}
if(a > inf / b){
int tot = 0;
for(int i = 0; i < n; i++){
int len = r[i] - l[i] + 1;
tot += len;
}
cout<<tot<<endl;
return 0;
}
int per = a * b;
bool all = 0;
map<int, int> upd;
set<int> ste;
for(int i = 0; i < n; i++){
int df = (r[i] / per) - (l[i] / per);
int lmod = l[i] % per;
int rmod = r[i] % per;
ste.insert(lmod);
if(rmod != a*b-1) ste.insert(rmod+1);
if((r[i] - l[i] + 1) >= per) all = 1;
else if(df == 1){
upd[lmod]++;
upd[0]++;
if(rmod != a*b-1) upd[rmod+1]--;
}
else{
upd[lmod]++;
if(rmod != a*b-1) upd[rmod+1]--;
}
}
ste.insert(0);
ste.insert(a*b-1);
if(all){
cout<<a*b<<endl;
}
else{
int ans = 0, delt = 0, lst = 0;
for(auto itr: ste){
if(delt > 0){
ans += (itr - lst);
}
delt += upd[itr];
lst = itr;
}
if(delt > 0) ans++;
cout<<ans<<endl;
}
return 0;
}
