#include<fstream>
#include<queue>
#include<algorithm>
#include<vector>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
int n, X, L, fear, val;
long long sol;
pair<int,int> A;
priority_queue< pair<int,int>, vector< pair<int,int> >, less< pair<int,int> > > q;
int main(){
    fin >> n >> X >> L;
    for( int i = 1; i <= n; i++ ){
        fin >> A.second >> A.first;
        q.push( A );
    }
    while( !q.empty() ){
        while( !q.empty() && X < (val = q.top().second) + fear )
            q.pop();
        if( !q.empty() ){
            sol += q.top().first;
            q.pop();
        }
        fear += L;
    }
    fout << sol << "\n";
    return 0;
}