package main

import (
	"fmt"
)

func main() {
	var n, m int
	fmt.Scan(&n, &m)
	a := make([]int, n)
	for i := 0; i < n; i++ {
		a[i] = n - i
	}
	for i := 0; i < m; i++ {
		var x int
		fmt.Scan(&x)
		x = n - x
		var b int
		b = a[x]
		a = append(a[:x], a[x+1:]...)
		a = append(a, b)
	}
	fmt.Println(a[n-1])
}