#include <bits/stdc++.h>

using namespace std;
ifstream f("branza.in");
ofstream g("branza.out");
deque <long long> dq;
long long n,s,t,c[1000005],p[1000005];
int main()
{
    f >> n >> s >> t;
    for (int i=1; i<=n; i++ )
    {
       f >> c[i] >> p[i];
    }
    for (int i=1; i<=n; i++ )
    {
       while ( !dq.empty() && c[dq.back()]+s*(i-dq.back())>=c[i] )
       {
          dq.pop_back();
       }
       while ( !dq.empty() && t<(i-dq.front()) )
       {
          dq.pop_front();
       }
       sl=sl+c[dq.front()]*p[i]+p[i]*(i-dq.front())*s;
    }
    return 0;
}