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


int main(int argc, char** argv) {
	if (argc != 2) {
		fputs("Usage: ", stdout);
		fputs(argv[0], stdout);
		fputs(" <input file>\n", stdout);
		return 1;
	}

	FILE* file = fopen(argv[1], "r");

	unsigned int safe_count = 0;

	const int max_length = 16;
	char buffer[17];
	int buf_length = 0;

	int line_no = 0;
	while (true) {
		bool first_number = true;
		int last_number = INT_MIN;
		int last_delta = 0;
		bool safe = true;
		int c;
		while (true) {
			c = fgetc(file);
			if (buf_length < max_length && c >= '0' && c <= '9') {
				buffer[buf_length] = c;
				buf_length++;
				continue;
			}

			if (buf_length > 0) {
				buffer[buf_length] = 0;
				int number = atoi(buffer);

				if (first_number) {
					first_number = false;
				} else {
					int delta = number - last_number;
					if (last_delta != 0 && delta * last_delta < 0) {
						safe = false;
					} else if (delta == 0 || abs(delta) > 3) {
						safe = false;
					}
					last_delta = delta;
				}

				last_number = number;
				buf_length = 0;
			}
			
			if (c == EOF || c == '\n') {
				break;
			}
		}

		if (safe && !first_number) {
			safe_count++;
		}
		line_no++;

		if (c == EOF) {
			break;
		}
	}

	printf("Safe count: %d\n", safe_count);

	fclose(file);
}