void Solve(StreamScanner ss, StreamWriter sw)
{
//---------------------------------
var N = ss.Next(int.Parse);
var T = ss.Next(long.Parse);
var Tn = ss.Next(long.Parse, N);
var ans = T;
for (var i = 1; i < N; i++)
{
ans += Math.Min(T, Tn[i] - Tn[i - 1]);
}
sw.WriteLine(ans);
//---------------------------------
}