#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>

#define LINES 1000

// power! x to the y!
int pow(int x, int y)
{
	int ans = 1;
	for (int i = 0; i < y; i++) ans *= x;
	return ans;
}
// parse string into array of numbers
int parse_numbers(char *str_row, int *row, int n)
{
	int i = 0;
	for (; str_row[i] != '\n'; i++);
	for (; i >= 0; i--) {
		int pos = 0;
		for (; str_row[i] >= '0' && str_row[i] <= '9' && i >= 0; i--) {
			row[n] += (str_row[i] - '0') * pow(10, pos);
			pos++;
		}
		n--;
	}

	return 1;
}
// check if specific report is safe
int check_report(int *row, int len)
{
	// read number. Compare next number (higher, lower, +-1-2)
	// if you get to row[i + 1]line, ++
	bool rising = 0;
	bool first = 1;
	for (int i = 0; i < len - 1; i++) {
		// if difference isnt 1-3
		if (abs(row[i + 1] - row[i]) > 3 || abs(row[i + 1] - row[i]) < 1)
			return 0;
		// only for first comparison of row. Set direction.
		if (first && ((row[i + 1] - row[i]) < 0))
			rising = 0;
		else if (first)
			rising = 1;
		// for other comparisons, compare current direction to the previous.
		if (!first && (rising != !((row[i + 1] - row[i]) < 0))) {
			// printf("rising: %d while %d - %d is %d\n", rising, row[i + 1], row[i], row[i + 1] - row[i]);
			return 0;
		}
		// get ready for the next comparisons!
		first = 0;
	}
	return 1;
}

int dampener(int *row, int len)
{
	if (check_report(row, len))
		return 1;

	for (int i = 0; i < len; i++) {
		int *dampened_row = malloc((len - 1) * sizeof(int));
		// initialize shorter array, but skip element i
		bool skipped = 0;
		for (int j = 0; j < len - 1; j++) {
			if (j != i && !skipped) {
				dampened_row[j] = row[j];
			}
			else {
				dampened_row[j] = row[j + 1];
				skipped = 1;
			}
		}
		if (check_report(dampened_row, len - 1)) {
			free(dampened_row);
			return 1;
		}
		free(dampened_row);
	}

	return 0;
}

int main()
{
	int safe = 0;
	// read input row into array, count elements
	FILE *input;
	input = fopen("./input", "r");
	char line[32];
	for (int i = 0; i < LINES; i++) {
		// get string (line), count numbers, put into int array (row)
		int numbers = 1;
		fgets(line, sizeof(line), input);
		// count number of numbers, allocate memory
		for (int c = 0; line[c]; c++) numbers += (line[c] == ' ');
		int *row = (int *)calloc(numbers, sizeof(int));
		// parse numbers into array
		parse_numbers(line, row, numbers);
		// for (int j = 0; j < numbers; j++) printf("%d ", row[j]);
		// printf("\n\n");

		// send elements and length to check_report, add result to sum
		safe += dampener(row, numbers);
		free(row);
	}

	printf("%d\n", safe);
}