#include <stdio.h>

void strconv(char *s)
{
  while (*s != '\0') { 
    if ('a' <= *s && *s <= 'z') {
      *s = *s - 'a' + 'A';
    }
    else if ('A' <= *s && *s <= 'Z') {
      *s = *s - 'A' + 'a';
    }
    s++;
  }
}

int main(void)
{
  char str[128];

  printf("string? ");
  scanf("%s", str);

  printf("%s => ", str);
  strconv(str);
  printf("%s\n", str);

  return 0;
}