#include <stdio.h>

void main(void) {
	int n = 0 ,w = 0 ;
	scanf("%d %d",&n,&w);
	int capacity = 0 , weight = 0 , maxCapacity = 0;
	for ( int i = 0 ; i < n ; i++ ){
		
		scanf("%d %d",&capacity ,&weight);
		if(w < weight){
			continue;
		}
		if(capacity > maxCapacity){
			maxCapacity = capacity;
		}
	}
	int selectKnapsack = -1;
	if(maxCapacity != 0){
		selectKnapsack = maxCapacity;
	}
	printf("%d",selectKnapsack);
}