int main()
{
 int a,b,c,t,t1,t2;
 char q;
 a=0;
 b=0;
 t2=0;
 scanf("%d%c",&t1,&q);
 while (q==',')
 {
	 a++;
     scanf("%d%c",&c,&q);
     if (c>=t1)		 
     {
       if (c==t1)
		   b=b+1;
	   else {
		     t=t1;
             t1=c;
             t2=t;
	   }
     }
	 else if (c>t2)t2=c;	
 }
 if ((a==b)||(a==0))printf("No\n"); 
 else printf("%d",t2);
 return 0;
}