Problem:
Score : 300 points

Problem Statement

There is an empty array.
The following N operations will be performed to insert integers into the array.
In the i-th operation (1≤i≤N), b_i copies of an integer a_i are inserted into the array.
Find the K-th smallest integer in the array after the N operations.
For example, the 4-th smallest integer in the array \{1,2,2,3,3,3\} is 3.

Constraints

1≤N≤10^5

1≤a_i,b_i≤10^5

1≤K≤b_1…+…b_n

All input values are integers.

Input

Input is given from Standard Input in the following format:

N K
a_1 b_1
:
a_N b_N

Output

Print the K-th smallest integer in the array after the N operations.

Sample Input 1

3 4
1 1
2 2
3 3

Sample Output 1

3

The resulting array is the same as the one in the problem statement.

Sample Input 2

10 500000
1 100000
1 100000
1 100000
1 100000
1 100000
100000 100000
100000 100000
100000 100000
100000 100000
100000 100000

Sample Output 2

1

Solution in Lua (5.3.2) (judge verdict: Accepted)

local N, K = io.read("n", "n")
local t = {}
local keys = {}
for i=1,N do
    local a, b = io.read("n", "n")
    if t[a] then
        t[a] = t[a] + b
    else
        t[a] = b
        table.insert(keys, a)
    end
end
table.sort(keys)
local c = 0
for _,k in ipairs(keys) do
    c = c + t[k]
    if c >= K then
        print(k)
        break
    end
end