#include <bits/stdc++.h>

using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");

struct credite
{
    long long nrC, timp;
};

priority_queue<long long> q;

credite v[10001]= {0};

int main()
{
    int n,X,L;
    fin>>n>>X>>L;
    int p=0;
    for(int i=1; i<=n; i++)
    {
        int x,y;
        fin>>x>>y;
        v[++p].nrC=y;
        v[p].timp=x;
    }
    int mx=v[1].timp;
    int cnt=n%L;
    long long s=0;
    for(int i=0; i<=X; i=i+1)
    {
        for(int j=1; j<=n; j++)
        {
            if(v[j].timp==i)
            {
                q.push(v[j].nrC);
            }
        }
        if(i%L==cnt)
        {
            s=s+q.top();
            q.pop();
        }
    }
    fout<<s;
    return 0;
}