#include <stdio.h>
struct ab{
	int id;
	int first;
	int second;
}abc[50000];
int cmp1(const void *a, const void *b){
	return ((struct ab *)a)->first - ((struct ab *)b)->first;
}
int cmp2(const void *a, const void *b){
	return ((struct ab *)a)->second - ((struct ab *)b)->second;
}


int main()
{
	int n,k, i;

	scanf("%d%d", &n,&k);
	for(i = 0; i < n; i++){
		scanf("%d%d",&abc[i].first, &abc[i].second);
		abc[i].id = i +  1;
	}
	qsort((void *)abc, n,sizeof(abc[0]),cmp1);
	qsort((void *)(&abc[n - k]), k,sizeof(abc[0]),cmp2);
	printf("%d\n", abc[n-1].id);
	return 0;
}