function main(input) {
  const n = Number(input[0]);
  const bit = input[1].split(" ");
  let ans = 0;
  for(let i=0; i<n; i++) {
    ans += move(bit, i);   
  }
  console.log(ans);
}

function move(bit, i) {
  let j = i;
  while(true) {
    if(bit[j] === "0" || j === (bit.length-1)) break;
    if(bit[j+1] === "1") { j+=1; break; }
    j+=2;
  }
  return j-i;
}

main(require("fs").readFileSync("/dev/stdin", "utf8").split("\n"));