#include <stdio.h>

int main(void)
{
	int pull_out,card[50],save;
	int i,j,N,M;
	scanf("%d %d",&N,&M);
	
	for(i=0; i<N; i++){
		card[i]=i+1;
	}
	
	for(i=0; i<M; i++){
		scanf("%d",&pull_out);
		save = card[0];
		card[0] = card[pull_out - 1];
		card[pull_out] = save;
	}
	printf("%d\n",card[0]);
	return 0;
}