import std.stdio;
import std.algorithm;
import std.math;
import std.conv;
import std.string;

T readNum(T)(){
  return readStr.to!T;
}

T[] readNums(T)(){
  return readStr.split.to!(T[]);
}

string readStr(){
  return readln.chomp;
}

void main(){
  auto n = readNum!int;
  auto b = readNums!int;
  int ret;

  foreach(i; 0 .. n-2){
    ret += min(b[i], b[i+1]);
  }

  ret += b[0];
  ret += b[n-2];

  writeln(ret);
}
