'use strict';
const main = val => {
  const n = parseInt(val[0], 10);
  let b = val[1].split(' ').map(p => parseInt(p, 10));
  let c = new Array(n);
  c[0] = b[0], c[n-1] = b[n-2];
  for (let i = 0; i < b.length-1; i++) {
    c[i+1] = Math.min(b[i], b[i+1]);
  }
  var ans = c.reduce((x,y) => x+y);
  console.log(ans);
  
}
main(require("fs").readFileSync("/dev/stdin", "utf8").split('\n'));