276A.cc

#include<bits/stdc++.h>
#define   ll                           		long long int
#define   ull                           	unsigned long long int
#define   cint                              const int
#define   fo(number1,number2,number3)  		for(int number1=number2;number1<number3;++number1)
#define   rfo(number1,number2,number3) 		for(int number1=number2-1;number1>=number3;--number1)
#define   pi                          		pair<int,int>
#define   vLL                          		vector<ll>
#define	  vi								vector<int>
#define   pb                          		push_back
#define   ppb                               pop_back
#define   eb 								emplace_back
#define   lbd								lower_bound
#define   ubd								upper_bound
#define   mp                          		make_pair
#define   cps                         		CLOCKS_PER_SEC
#define   decimal(k)                  		fixed<<setprecision(k)
#define   PI                          		3.14159265359
#define   fastio                      		ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define   ff                           		first
#define   ss                           		second
#define   all(V)                      		(V).begin(),(V).end()
#define   alla(a,n) 						a, a+n
#define   sz(v) 							(ll)v.size()
#define   SORT(v) 							sort(all(v))
#define   REV	 							reverse
#define   SUM(v) 							accumulate(v.begin(),v.end(),0)
#define   MAX 								max_element
#define   MIN	 							min_element
#define   UNIQUE(v) 						SORT(v); v.erase(unique(v.begin(),v.end()),v.end())
#define   UNIQUEA(a,n) 						unique(a,a+n)-a
#define   MAXA(a,n) 						max_element(a,a+n)
#define   MINA(a,n) 						min_element(a,a+n)
#define   SORTA(a, n) 						sort(alla(a, n))
#define   REVA(a, n) 						reverse(alla(a, n))
#define   mem1(a)           				memset(a,-1,sizeof(a));
#define   mem0(a)           				memset(a,0,sizeof(a));
#define   mymax                       		1000000000000000100
#define   mymin                      		-1000000001
#define   bitcount                    		__builtin_popcount
#define   gcd                         		__gcd
#define   MOD                         		(ll)1000000007
#define   TEST(t) 					  		int tc; cin>>tc; fo(t,1,tc)
#define   VECT(v,n)							ll n; cin >> n; vLL v(n); fo(i,0,n-1) cin >> v[i];
#define   NUM(n)							ll n; cin >> n;
#define	  STRING(s)							string s; cin >> s;
#define   TS								to_string
#define   len(s)							(s).length()
#define   line 						  		cout << "\n";
#define   el								"\n"
#define   clkstart							auto start = high_resolution_clock::now();
#define   clkend							auto stop = high_resolution_clock::now(); auto duration = duration_cast<microseconds>(stop - start);
#define   TIME								line; line; cout << "Time taken by function: " << duration.count()/1e6 << " seconds" << endl;
#define   open								{
#define	  close								}
#define   goog(tno)                         cout <<"Case #" << tno << ": "
#define   deb(x)							cout << #x << " = " << x << el;
#define   deb2(x,y)							cout << #x << " = " << x << " : " << #y << " = " << y << el;
// #ifndef SEGMENTTREE_H
#define SEGMENTTREE_H
#define left(i) (2*i + 1)
#define right(i) (2*i + 2)
#define parent(i) ((i-1)/2)
using namespace std;
// bool is_perfect_square(ll n) {
//     if (n < 0)
//         return false;
//     ll root(round(sqrt(n)));
//     return n == root * root;
// }
// bool isPrime(ll N) {                 // a good enough deterministic prime tester
//   if (N <= _sieve_size) return bs[N];                   // O(1) for small primes
//   for (int i = 0; i < (int)primes.size(); i++)
//     if (N % primes[i] == 0) return false;
//   return true;                    // it takes longer time if N is a large prime!
// }
int main()
{
    ll n,k,a;
    cin>>n>>k;
    ll ans=INT_MIN;
    while(n--){
        ll fi,ti;
        cin>>fi>>ti;
        if(ti>k)
        a=fi-(ti-k);
        else
        a=fi;
        ans=max(ans,a);
    }
    cout<<ans;
}