#include<fstream>
#include<vector>
using namespace std;
int main ()
{
    ifstream in("lupul.in");
    ofstream out("lupul.out");
    int n,x,l,sum=0,a,b;
    in>>n>>x>>l;
    vector<vector<int>> v;
    v.reserve(100005);
    for(int i=1;i<=n;i++)
    {
        in>>a>>b;
        v[a].push_back(b);
    }
    while(x>=0)
    {
        int max=0;
        for(int i=(x-l+1>=0 ? x-l+1:0) ; i<=x; i++)
            for(int j=0;j<v[i].size();j++)
                if(v[i][j]>max)
                    max=v[i][j];
        sum+=max;
        x-=l;
    }
    out<<sum;
}