C : Caesar Cipher

#include <stdio.h>

void encrypt(int shift);

int main(void)
{
 int shift;
 int decOrEnc;
 
 printf("Amount of shifts: ");
 scanf("%d", &shift);
 if (shift < 0)
 {
  printf("Bad Input.");
  return 0;
 }
 printf("Type 1 to encrypt or 0 to decrypt: ");
 scanf("%d", &decOrEnc);
 if (decOrEnc != 0 && decOrEnc !=1)
 {
  printf("Bad Input.");
  return 0;
 }
 while(getchar() != '\n');
 if (decOrEnc == 1)
  encrypt(shift);
 else
 {
  shift = -1 * shift;
  encrypt(shift);
 }
 return 0;
}

void encrypt(int shift)
{
 char ch;
 printf("Please enter a string: ");
 ch = getchar();
 while(ch != '\n')
 {
  if (ch == ' ')
   putchar(ch);
  else
  {
   if(shift == 1)
    putchar(ch + shift);
   else
    putchar(ch - shift);
  }
  ch = getchar();
 }
 putchar(ch);
}