Calculate a firsts numbers

I have a program but this don't work, this programe had to calculate a firsts numbers of a serie, thanks.

#include <stdio.h>
#include <string.h>
#include <math.h>
void main()
{
        char c[255];
      long int m=1,cont1,cont2,b=2;
        printf("\n Tria si vols imprimir una llista de nombre parells,\n o una llista de nombres primers: ");
      scanf("%s",&c);
      printf("\nIntrodueix el primer numero de la serie: ");
      scanf("%ld",&cont1);
      printf("\nIntrodueix el segon numero de la serie: ");
      scanf("%ld",&cont2);
      if (!strcmp (c,"primers")){
            while (cont1<cont2){
                  while ((b>(cont1/2)) && (m!=0)){
                  if((cont1%b)!=0) b=b+1;
                  if((cont1%b)==0) m=0;
                  }
                  if (m==0){
                         printf("\nEl nombre %ld és primer",cont1);
                         m=1;
                         }
                  ++cont1;
                  }
      }
      if (!strcmp (c,"parells")){
            if((cont1%2)!=0) ++cont1;
            while (cont1<cont2){
                  printf("%ld\n", cont1);
                  ++cont1;
                  ++cont1;
                  }
              if((cont2/2)==0) printf("%ld",cont2);
      }        
}
FxSedgeAsked:
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SteHCommented:
Is this homework? I guess yes, so I give just hints:
put the line
printf ("%d %d %d\n", cont1, b, m);
after while (cont1<cont2) and look whether the values are as you expect.

Another thing:

 if (test != 0) do1;
 if (test == 0) do2;

can be rewritten as

if (test != 0)
     do1;
else
     do2;
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