#include //#include using namespace std; //using namespace atcoder; //using mint = modint1000000007; //const int mod = 1000000007; //using mint = modint998244353; //const int mod = 998244353; //const int INF = 1e9; const long long LINF = 1e18; //const bool debug = false; #define rep(i, n) for (int i = 0; i < (n); ++i) #define rep2(i,l,r)for(int i=(l);i<(r);++i) #define rrep(i, n) for (int i = (n-1); i >= 0; --i) #define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i) #define all(x) (x).begin(),(x).end() #define allR(x) (x).rbegin(),(x).rend() #define endl "\n" #define P pair template inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int n, d; cin >> n >> d; vectorp(n), q(n); rep(i, n)cin >> p[i] >> q[i]; long long ans = -LINF; rep(i, n)rep(j, n) { if (i == j)continue; long long anssub = LINF; long long x = (q[i] - p[i]) + (q[j] - p[j]); if (x >= 0) { chmin(anssub, -p[i]); chmin(anssub, -p[i] + q[i] - p[j]); } else { { long long sub = -p[i]; sub += x * ((d - 1) / 2); chmin(anssub, sub); } { long long sub = -p[i] + q[i] - p[j]; sub += x * ((d - 2) / 2); chmin(anssub, sub); } } chmax(ans, anssub); } cout << ans << endl; return 0; }