609 B | 609 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
BLANK = " "
inp = input
# inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
N, K = mii()
l = [[_]+mii() for _ in range(N)]
l.sort(key=lambda t:-t[1])
l = l[:K]
l.sort(key=lambda t:-t[2])
p(l[0][0] + 1)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()