/**
*/
#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
const int nmax=100010;
vector <int> v[nmax];
long long int sum;
priority_queue <int> q;
int main()
{
    int n,x,l,d,c;
    fin>>n>>x>>l;
    for(int i=1;i<=n;i++)
    {
        fin>>d>>c;
        if(d<=x)
            v[(x-d)/l+1].push_back(c);
    }
    for(int i=x;i>=1;i--)
    {
        for(int j=0;j<v[i].size();j++)
        {
            q.push(v[i][j]);
        }
        if(!q.empty())
        {
            sum=sum+q.top();
            q.pop();
        }
    }
    fout<<sum;
   return 0;
}