#include<algorithm>
#include<bitset>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<deque>
#include<fstream>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<utility>
#include<vector>

using namespace std;

#define dbg(x) (cout<<#x<<" = "<<(x)<<'\n')
const string problemName = "lupu";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";

typedef long long int lld;
typedef pair<int, int> PII;

const int INF = (1LL << 31) - 1;
const lld LINF = (1LL << 62) - 1;
const int NMAX = 100000 + 5;

int N, X, L;
lld sol;
int T[NMAX];
int D[NMAX];
int A[NMAX];
int P[NMAX];
priority_queue<int> PQ;

struct cmp {
    bool operator()(const int &A, const int &B) const {
        return T[A] > T[B];
    }
};

int main() {
    int i, j;

#ifndef ONLINE_JUDGE
    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);
#endif

    scanf("%d%d%d", &N, &X, &L);

    for(i = 1; i <= N; i++) {
        scanf("%d%d", &D[i], &A[i]);
        T[i] = 1 + max(-1, (X - D[i]) / L);
        P[i] = i;
    }

    sort(P + 1, P + N + 1, cmp());

    for(i = j = 1; i <= N; i = j) {
        for(j = i; T[P[i]] == T[P[j]] && j <= N; j++)
            PQ.push(A[P[j]]);

        sol += 1LL * PQ.top();
        PQ.pop();
    }

    printf("%lld\n", sol);

    return 0;
}