/* ECP: FILEname=fig3_28.c */
/* 1*/   /* Find Next Prime After StartingNumber */

/* 2*/   #include <stdio.h>

/* 3*/   main( void )
/* 4*/   {
/* 5*/       unsigned long int Divisor, PossiblePrime;

/* 6*/       printf( "Enter the starting number: " );
/* 7*/       scanf( "%lu", &PossiblePrime );

/* 8*/       if( PossiblePrime <= 2 )
/* 9*/           PossiblePrime = 2;
/*10*/       else
/*11*/       if( PossiblePrime != 3 )
/*12*/       {
/*13*/           if( PossiblePrime % 2 == 0 )
/*14*/               PossiblePrime++;	/* Need An Odd Number */
/*15*/       
/*16*/           for( ; ; PossiblePrime += 2 )
/*17*/               for( Divisor = 3; PossiblePrime % Divisor; Divisor += 2 )
/*18*/                   if( Divisor * Divisor > PossiblePrime )
/*19*/                       goto FoundPrime;
/*20*/       }

/*21*/   FoundPrime:
/*22*/       printf( "Next largest prime is %lu\n", PossiblePrime );
/*23*/   }