SwapCase

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define N 5
int main(void) {
  char *input = (char *) malloc(N);
  int count = 0;
  int size = 1;
  while (1) {
    if (count >= size * N) {
      char *new = (char *) malloc(++size * N);
      input = strcpy(new, input);
    }
    char c;
    if ((c = (char) getchar()) == '\n') break;
    input[count++] = c;
    input[count] = '\0';
  }
  for (int i = 0; input[i]; i++) {
    char c = input[i];
    if (islower(c)) putchar(toupper(c));
    else if (c) putchar(tolower(c));
    else putchar(c);
  }
  puts("");
  return 0;
}