Maximal Value

AtCoder

IDabc140_c

Time2000ms

Memory256MB

Difficulty—

There is an integer sequence $A$ of length $N$ whose values are unknown. Given is an integer sequence $B$ of length $N-1$ which is known to satisfy the following: $B_i \geq \max(A_i, A_{i+1})$ Find the maximum possible sum of the elements of $A$. ## Constraints * All values in input are integers. * $2 \leq N \leq 100$ * $0 \leq B_i \leq 10^5$ ## Input Input is given from Standard Input in the following format: $N$ $B_1$ $B_2$ $...$ $B_{N-1}$ [samples]

Samples

Input #1

3
2 5

Output #1

9

$A$ can be, for example, ( $2$ , $1$ , $5$ ), ( $-1$ , $-2$ , $-3$ ), or ( $2$ , $2$ , $5$ ). Among those candidates, $A$ = ( $2$ , $2$ , $5$ ) has the maximum possible sum.

Input #2

2
3

Output #2

Input #3

6
0 153 10 10 23

Output #3

API Response (JSON)

{
  "problem": {
    "name": "Maximal Value",
    "description": {
      "content": "There is an integer sequence $A$ of length $N$ whose values are unknown. Given is an integer sequence $B$ of length $N-1$ which is known to satisfy the following: $B_i \\geq \\max(A_i, A_{i+1})$ Find th",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc140_c"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "There is an integer sequence $A$ of length $N$ whose values are unknown.\nGiven is an integer sequence $B$ of length $N-1$ which is known to satisfy the following:\n$B_i \\geq \\max(A_i, A_{i+1})$\nFind th...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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