#include <stdio.h>

int main() {
  int n, m;
  scanf("%d %d", &n, &m);

  int arr[n+1], i;
  for (i=0; i<=n; i++) {
    arr[i]=i;
  }

  for (;m--;) {
    int a;
    scanf("%d", &a);

    arr[0]=arr[a];
    for (i=a; a>0; a--) {
      arr[a]=arr[a-1];
    }
  }

  printf("%d\n", arr[1]);
  return 0;
}