#include <cstdio>
#include <queue>
#include <cstring>
#include <algorithm>
#include <vector>
#include <cassert>
#include <map>
#include <set>
using namespace std;
typedef long long LL;

#ifdef INFOARENA
#define ProblemName "lupu"
#endif

#define MCONCAT(A, B) A B
#ifdef ProblemName
#define InFile MCONCAT(ProblemName, ".in")
#define OuFile MCONCAT(ProblemName, ".out")
#else
#define InFile "fis.in"
#define OuFile "fis.out"
#endif
typedef long long LL;

map< int, vector<int> > M;

inline int getTura(int X, int K, int d) {
	int z = (X - d) / K;
	return z;
}

int main() {
	freopen(InFile, "r", stdin);
	freopen(OuFile, "w", stdout);
	int N, X, L;
	scanf("%d%d%d", &N, &X, &L);
	for (int i = 0; i < N; ++i) {
		int d, a;
		scanf("%d%d", &d, &a);
		int t = getTura(X, L, d);
		if (t < 0) continue;
		M[t].push_back(a);
	}
	int prv = -1, take = 0;
	LL ans = 0;
	for (auto &it : M) {
		take += it.first - prv;
		prv = it.first;
		sort(it.second.rbegin(), it.second.rend());
		int canTake = min(take, (int)it.second.size());
		take -= canTake;
		for (int i = 0; i < canTake; ++i)
			ans += it.second[i];
	}
	printf("%lld\n", ans);
	return 0;
}