N,B=map(int,raw_input().split())
XYP=[map(int,raw_input().split()) for i in range(N)]
xlist=[x for x,y,p in XYP]
ylist=[y for x,y,p in XYP]
xlist=list(set(xlist))
ylist=list(set(ylist))
xlist.sort()
ylist.sort()
unZipX={x:i for i,x in enumerate(xlist)}
unZipY={y:i for i,y in enumerate(ylist)}
ptable=[ [0 for i in range(len(unZipY)+1)] for j in range(len(unZipX)+1)]
ntable=[ [0 for i in range(len(unZipY)+1)] for j in range(len(unZipX)+1)]
for x,y,p in XYP:
    ptable[unZipX[x]+1][unZipY[y]+1]=p
    ntable[unZipX[x]+1][unZipY[y]+1]=1
for i in range(1,len(unZipX)+1):
    for j in range(1,len(unZipY)+1):
        ptable[i][j]=ptable[i][j]+ptable[i][j-1]+ptable[i-1][j]-ptable[i-1][j-1]
        ntable[i][j]=ntable[i][j]+ntable[i][j-1]+ntable[i-1][j]-ntable[i-1][j-1]
ans = 0
for x in range(1,len(unZipX)+1):
    for X in range(x,len(unZipX)+1):
        Y=0
        for y in range(1,len(unZipY)+1):
            Y=max(Y,y-1)
            while Y+1<=len(unZipY) and ptable[X][Y+1]-ptable[X][y-1]-ptable[x-1][Y+1]+ptable[x-1][y-1] <= B:
                Y+=1
            if Y>=y:
                #print xlist[x-1],"-",xlist[X-1],"*",ylist[y-1],"-",ylist[Y-1], ptable[X][Y]-ptable[X][y-1]-ptable[x-1][Y]+ptable[x-1][y-1], ntable[X][Y]-ntable[X][y-1]-ntable[x-1][Y]+ntable[x-1][y-1] 
                ans = max(ans, ntable[X][Y]-ntable[X][y-1]-ntable[x-1][Y]+ntable[x-1][y-1])
print ans