#include <iostream>
#include <cstdio>
#include <vector>
#include <string>
#include <cstring>
#include <algorithm>
using namespace std;

#ifdef LOCAL
	#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
	#define eprintf(...) 42
#endif


const int maxt = 1e7 + 1e6;
const int N = (int)1e5 + 100;
int ga[2][N];
long long gans[2][2 * N];
long long inf = 1e18;


long long dOnPrefix[2 * N];
int inQ[maxt];

int st[maxt];
long long sumSt[maxt];
int sizeSt;

int getA(int a[], int idx)
{
	if (idx >= N) return 0;
	return a[idx];
}

int getGA(int type, int idx)
{
	if (idx >= N) return 0;
	return ga[type][idx];
}

void addSt(int x)
{
	st[sizeSt] = x;
	sumSt[sizeSt] = x;
	if (sizeSt != 0)
		sumSt[sizeSt] += sumSt[sizeSt - 1];
	sizeSt++;
	if (sizeSt >= maxt)
		throw 42;
}
void takeSt(int cnt)
{
	sizeSt -= cnt;
}
long long costSt(int cnt)
{
	return sumSt[sizeSt - 1] - sumSt[sizeSt - cnt - 1];
}

void solve(int n1, int n2, int a[], long long ans[] )
{
	memset(dOnPrefix, 0, sizeof dOnPrefix);
	memset(inQ, 0, sizeof inQ);

	long long d = 0;
	int inq = 0;
	int mt = maxt / n2;
	for (int i = 0; i < N; i++)
	{
		dOnPrefix[i] = d;
		inQ[i] = inq;
		inq += a[i];
		d -= a[i] * 1LL * i;
		int x = min(inq, n1);
		d += x * 1LL * i;
		inq -= x;
	}

	long long sd = 0;
	sizeSt = 0;
	fprintf(stderr, "%d\n", mt * n2);
	for (int i = mt - 1; i >= 0; i--)
	{
		for (int j = 0; j < n2; j++)
		{
			addSt(i);
		}
		sd += costSt(getA(a, i) );
		sd -= i * 1LL * getA(a, i);
		takeSt(getA(a,i) );

		if (i < N)
		{
			ans[i] = sd + dOnPrefix[i] + costSt(inQ[i] );
		}
	}

	eprintf("inq: ");
	for (int i = 0; i < 10; i++)
		eprintf("%d ", inQ[i] );
	eprintf("\ndst: ");
	for (int i = 0; i < 10; i++)
		eprintf("%lld ", dOnPrefix[i] );
	eprintf("\n----------------------\n");
}


int main()
{
	freopen("lanes.in", "r", stdin);
#ifndef LOCAL
	freopen("lanes.out", "w", stdout);
#endif

	int n1, n2, m, r;
	scanf("%d%d%d%d", &n1, &n2, &m, &r);
	for (int i = 0; i < m; i++)
		scanf("%d%d", &ga[0][i], &ga[1][i] );
	solve(n1 + 1, n1, ga[0], gans[0] );
	solve(n2, n2 + 1, ga[1], gans[1] );

	for (int t = 0; t < 2; t++)
	{
		for (int i = 0; i < 2 * m; i++)
		{
			eprintf("%lld ", gans[t][i] );
		}
		eprintf("\n");
	}


	long long answer = inf;
	int pos = -1;
	for (int i = 0; i < m; i++)
	{
		long long cur = gans[0][i] + gans[1][i + r];
		eprintf("%d : %lld %lld\n", i, gans[0][i], gans[1][i + r] );
		if (cur < answer)
		{
			answer = cur;
			pos = i;
		}
	}
	printf("%d\n", pos + 1);

	return 0;
}