Write a c program to find out second largest element of an unsorted array.?

 #include<stdio.h>  
  #include<stdlib.h>  
  main()  
  {  
  int a[100],i,num,n,mx;  
 printf("enter number of elements to be entered");  
  scanf("%d",&n);  
  printf("enter numbers");  
  for(i=0;i<n;i++)  
  scanf("%d",&a[i]);  
 mx=a[0];  
 num=a[0];  
  for(i=0;i<n;i++)  
  {  
 if(a[i]>num)  
  {  
  if(a[i]>mx)  
  {num=mx;  
  max=a[i];}  
 if(a[i]<mx)  
  num=a[i];  
  }  
 }  
  printf("second largest no. is %d",num);  
  system("pause");  
 }