changing alphabet (string) order

[firipu]

i want to creat a new string with other alphabet order
for example instead of starting with a to start with r(order o 3)and end with abc

int main(void)
{
  char alf[]="abcdefghijklmnopqrstuvwxyz";
  char ncifra[ALF];
  int i,j,nchave;
  
  printf("Chave (posicoes a transpor):");
  scanf("%d",&nchave);
           
  for(i=nchave;i<ALF;i++) {
     j=0;
     ncifra[j]=alf[i];
     j++;
  }
  for(i=0;i<nchave;i++) {
     j=26-nchave;
     ncifra[j]=alf[i];
     j++;
  }
return 0;
}