#include<stdio.h>
int mystrlen ( char * );
main()
{
  char a[100]= "hello world";
  int len;
  len = mystrlen(a);        
  printf("%d \n", len);
  system("pause");    
}

int mystrlen ( char *s )
{
  int length = 0 ;
  while ( *s != '\0' )
  {
    length++ ;
    s++ ;
  }
  return ( length ) ;
}