#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
ll n, a, b; cin >> n >> a >> b;
ll ans = 0;
if(LONG_LONG_MAX/b <= a){
for(int i = 0; i < n; ++i){
ll l, r; cin >> l >> r;
ans+=r-l+1ll;
}
cout << ans << "\n";
return 0;
}
vector<array<ll,3>> inter;
for(int i = 0; i < n; ++i){
ll l, r; cin >> l >> r;
if((r/(a*b))-(l/(a*b)) >= 2 || ((r/(a*b))-(l/(a*b)) >= 1 && (r%(a*b)) >= (l%(a*b)))){
cout << a*b << "\n";
return 0;
}
if((r/(a*b))-(l/(a*b)) >= 1){
inter.push_back({0,l%(a*b),r%(a*b)});
}
else{
inter.push_back({1,l%(a*b),r%(a*b)});
}
}
sort(inter.begin(),inter.end());
pair<ll,ll> hi= {1ll,inter[0][2]};
if(inter[0][0] == 1){
ans = inter[0][1];
}
for(int i = 0; i < n; ++i){
if(inter[i][0] && !inter[0][0] && inter[i][1] >= inter[0][1])break;
if(inter[i][0] && inter[i][1] > hi.second+1){
ans += inter[i][1] - hi.second -1;
}
hi = max(hi,make_pair(1ll,inter[i][2]));
}
if(inter[0][0] == 1){
ans+=a*b-hi.second-1;
}
else{
ans+=max(0ll,inter[0][1]-hi.second-1);
}
cout << a*b - ans << "\n";
}
