'use strict';

function main(stdin) {
  const input = stdin.split('\n');
  const N = Number(input.shift());
  const params = input[0].split(' ').map(v => parseInt(v, 10));

  const a = [];
  for (let i = 0; i < N; ++i) a[i] = Infinity;

  params.forEach((b, i) => {
    a[i] = Math.min(b, a[i]);
    a[i + 1] = b;
  })
  
  console.log(a.reduce((a, b) => a + b));
}

main(require('fs').readFileSync('/dev/stdin', 'utf8').trim())