#19 WA了 QWQ 求助的哇

#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll a,v;
int k,n;
int main(){
	cin>>n>>k;
	ll minn=-INT_MAX;
	ll ans;
	for(int i=1;i<=n;i++){
		cin>>v>>a;
		if(a<k){
			ll s=(k-a+1)*v;
			if(s>minn){
				minn=s;
				ans=i;
			}
		}
	}
	cout<<ans<<endl;
	return 0;
}