from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline
def segfunc(x, y):
    return min(x,y)

ide_ele = float('inf')


class SegTree:
    """
    Segment Tree
    """

    def __init__(self, init_val, segfunc, ide_ele):
        """
        初期化

        init_val: 配列の初期値
        """
        n = len(init_val)
        self.segfunc = segfunc
        self.ide_ele = ide_ele
        self.num = 1 << (n - 1).bit_length()
        self.tree = [ide_ele] * 2 * self.num
        # 配列の値を葉にセット
        for i in range(n):
            self.tree[self.num + i] = init_val[i]
        # 構築していく
        for i in range(self.num - 1, 0, -1):
            self.tree[i] = segfunc(self.tree[2 * i], self.tree[2 * i + 1])

    def update(self, k, x):
        """
        k番目の値をxに更新

        k: index(0-index)
        x: update value
        """
        k += self.num
        self.tree[k] = x
        while k > 1:
            self.tree[k >> 1] = self.segfunc(self.tree[k], self.tree[k ^ 1])
            k >>= 1

    def query(self, l, r):
        """
        [l, r)のsegfuncしたものを得る

        l: index(0-index)
        r: index(0-index)
        """
        res = self.ide_ele

        l += self.num
        r += self.num
        while l < r:
            if l & 1:
                res = self.segfunc(res, self.tree[l])
                l += 1
            if r & 1:
                res = self.segfunc(res, self.tree[r - 1])
            l >>= 1
            r >>= 1
        return res


N,K,L,P = map(int,input().split())
AB = [tuple(map(int,input().split())) for _ in range(N)]
n = N//2
m = N-n
X,Y = AB[:n],AB[n:]
SX = defaultdict(lambda:[])
SY = defaultdict(lambda:[])
cost = []
value = []
for i in range(1<<n):
    
    t = 0
    c = 0
    v = 0
    
    for j in range(n):
        
        if (i>>j)&1:
            
            t += 1
            a,b = X[j]
            c += a
            v += b
    SX[c].append((t,v))
    value.append(v)

for i in range(1<<m):
    
    t = 0
    c = 0
    v = 0
    
    for j in range(m):
        
        if (i>>j)&1:
            
            t += 1
            a,b = Y[j]
            c += a
            v += b
    SY[c].append((t,v))
    value.append(v)
    
for k in SX.keys():
    cost.append(k)
for k in SY.keys():
    cost.append(k)
    
cost = sorted(list(set(cost)))
value = sorted(list(set(value)))

nc = len(cost)
nv = len(value)
cc = {x:i for i,x in enumerate(cost)}
cv = {x:i for i,x in enumerate(value)}


T = [SegTree([0]*(nv),lambda x,y:x+y,0) for _ in range(m+1)]
TT = [[0]*nv for _ in range(m+1)]
KX = list(SX.keys())
KY = list(SY.keys())
KX.sort(reverse=True)
KY.sort()
def cle(a,D):
    
    y = len(D)-1
    x = 0
    if D[x]>=a:
        return 0
        
    if D[y]<a:
        return y+1
    
    while y-x>1:
        mid = (y+x)//2
        if D[mid]<a:
            x = mid
        else:
            y = mid
    return y
add_flg = defaultdict(lambda:False)
y_idx = 0
ans = 0
for kx in KX:
    
    while (y_idx<len(KY)):
        
        if KY[y_idx]+kx >L:
            break
        if add_flg[y_idx]:
            y_idx += 1
            continue
        
        for t,v in SY[KY[y_idx]]:
            T[t].update(cv[v],TT[t][cv[v]]+1)
            TT[t][cv[v]] += 1
        add_flg[y_idx] = True
        y_idx += 1
    
    for xt,xv in SX[kx]:
        
        lv = cle(P-xv,value)
        if lv==nv:
            continue
        
        for i in range(0,max(0,K-xt+1)):
            
            ans += T[i].query(lv,nv)
print(ans)