void main(){
  import std.stdio, std.string, std.conv, std.algorithm;

  int n; long p;
  rd(n, p);
  auto h=readln.split.to!(long[]);

  auto rec=new long[][](n, 3);
  const R=0, L=1, JP=2;
  rec[1][L]=1_000_000_000_000_000_000;
  foreach(i; 1..n){
    rec[i][R]=min(rec[i-1][R], rec[i-1][JP])+max(0, h[i]-h[i-1]);
    if(i>=2) rec[i][L]=min(rec[i-1][L], rec[i-1][JP])+max(0, h[i-1]-h[i]);
    rec[i][JP]=min(rec[i-1][R], rec[i-1][L], rec[i-1][JP])+p;
  }

  writeln(reduce!(min)(rec[n-1]));
}

void rd(T...)(ref T x){
  import std.stdio, std.string, std.conv;
  auto l=readln.split;
  assert(l.length==x.length);
  foreach(i, ref e; x){
    e=l[i].to!(typeof(e));
  }
}