package main 

import ("fmt")

func main() {
    var sum, shf int
    fmt.Scan(&sum, &shf)
    cards := make([]int, sum)
    for i:=0; i<sum; i++ {
        cards[i] = 1 + i
    }
    
    for i:=0; i<shf; i++ {
        var whr int // 上から何番目か
        fmt.Scan(&whr)
        top := []int{cards[whr - 1]}
        //fmt.Println(top)
        cards = remove(cards, cards[whr-1])
        cards = append(top, cards...)
    } 
	fmt.Println(cards[0])
}

func remove(cards []int, card int) []int {
    result := []int{}
    for _, num := range cards {
        if num != card {
            result = append(result, num)
        }
    }
    //fmt.Println(result)
    return result
}