#include <stdio.h>
#include <malloc.h>

int main(void)
{
    FILE *fp = fopen("words.txt", "r");

	char *buffer;
	int   size;
	int h_size;

	fseek(fp, 0, SEEK_END);
	size = ftell(fp);

	buffer = malloc(size + 1);
	memset(buffer, 0, size + 1);

	fseek(fp, 0, SEEK_SET);
	fread(buffer, sizeof(char), size, fp);

	h_size = size - 1;
	for (int i = 0; i < (size - 1) / 2; i++)
	{
		char data       = buffer[i];
		buffer[i]       = buffer[h_size];
		buffer[h_size--] = data;
	}

	fwrite(buffer, size, 1, stdout);

	free(buffer);

	fclose(fp);
    return 0;
}