#include<iostream.h>
// for strspn, strlen
#include<strings.h>
// for atoi and exit
#include<stdlib.h>

// MaxInt.C
//  burton rosenberg March 29, 1997

// program to show arrays of pointers, the argc, argv interface
// from C programs and the command line, and the use of atoi
// and other string programs to make more robust input.

char * DIGITS = "0123456789" ;

void bailOut( char * progName ) 
{
   cout << "usage: " << progName  << " one-or-more-positive-integers" << endl ;
   exit(-1) ;
}

int main( int argc, char * argv[] ) 
{
   if ( argc<2 ) 
   {
      bailOut( argv[0] ) ;
   }

   int i, j, maxSoFar  ;
   maxSoFar = -1 ;
   for ( i=1; i<argc; i++ ) {
      if ( strspn( argv[i], DIGITS ) != strlen(argv[i]) ) 
      {
          bailOut( argv[0] ) ;
      }
      j = atoi(argv[i]) ;
      if ( j > maxSoFar ) 
      {
         maxSoFar = j ;
      }
   }

   cout << maxSoFar << endl ;
   return 0 ;

}