#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
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-l+1 >= 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());
ll hi= 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+1){
ans += inter[i][1] - hi -1;
}
hi = max(hi,inter[i][2]);
}
if(inter[0][0] == 1){
ans+=a*b-hi-1;
}
else{
ans+=max(0ll,inter[0][1]-hi-1);
}
cout << a*b - ans << "\n";
}
