#include<iostream>
#include<algorithm>
using namespace std;
struct Node{
int id,a1,a2;
}vote[50005];
bool cmp(struct Node v1,struct Node v2){
return v1.a1>v2.a1;
}
int main(){
int n,k,ans,ansi;
scanf("%d%d",&n,&k);
for(int i=0;i<n;i++){
scanf("%d%d",&vote[i].a1,&vote[i].a2);
vote[i].id = i+1;
}
sort(vote,vote+n,cmp);
// for(int i=0;i<k;i++){
// cout<<vote[i].a1<<" "<<vote[i].a2<<endl;
// }
ans = vote[0].a2;
ansi = vote[0].id;
for(int i=1;i<k;i++)
if(vote[i].a2>ans){
ans = vote[i].a2;
ansi = vote[i].id;
}
printf("%d\n",ansi);
return 0;
}