function Main(input) {
  input = input.split("\n");
  var N = input[0];
var LineB = input[1].split(" ").map(Number);
  LineB.push(Infinity)
var Sum = 0;
for(var i=0; i<N-1 ; i++){
  if(LineB[i]<LineB[i+1]){
    Sum += LineB[i];
  }else{
    Sum += LineB[i+1];
  }
}
  console.log(Sum);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
