int main()
{
	int n=1,i=1,max1=0,max2=0,k=0;                //n??????
	int a[999];
	char c;
	
	scanf("%d%c",&a[0],&c);
	
	while (c==',')                     //23????N=23
	{
		scanf("%d%c",&a[i],&c);
		n++;
		i++;
	}
	//printf("%d %c",a[1],c);   //????????

    max1=a[0];
	for (i=0;i<n;i++)
	{
		if (a[i]!=max1)
			k=k+1;

		if (a[i]>=max1)
		{
			if(a[i]>max1)
			{
				max2=max1;
			}
			max1=a[i];
		}
		else
		{
			if (a[i]>max2)
			max2=a[i];
		}
	}

	if (k==0)
	{
		printf("No");
	}
	else
	printf("%d",max2);
	return 0;
}
