#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
using namespace std;
int n,k;
struct hs{int a,b,p;}f[50010];
bool bk1(hs a1,hs a2){return a1.a>a2.a;}
bool bk2(hs a1,hs a2){return a1.b>a2.b;}
int main(){
	freopen("elect.in","r",stdin); 
	freopen("elect.out","w",stdout);
	scanf("%d%d",&n,&k);
	for(int i=1;i<=n;i++){scanf("%d%d",&f[i].a,&f[i].b);f[i].p=i;}
	sort(f+1,f+1+n,bk1);
	sort(f+1,f+1+k,bk2);
	printf("%d",f[1].p);
	return 0;
}