Changing case of string characters

#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char str[30];
int i=0,len;
clrscr();
printf("Enter any string\n");
gets(str);
len=strlen(str);
printf("\nOriginal String:\t");
puts(str);
printf("\nString with case changed:\t");
while(i<len)
{
    if(str[i]>='a'&&str[i]<='z')
    {
       printf("%c",str[i]-32);
    }
else
  {
   if(str[i]>='A'&&str[i]<='z')
    {
      printf("%c",str[i]+32);
    }
   else
     {
     printf("%c",str[i]);
     }
  }
  i++;
}
getch();
}


OUTPUT:

Enter any string

Tushar

Original String:    Tushar

String with case changed:   tUSHAR