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


int
main()
{
	int cycle;
	char buf[BUFSIZ];
	char * op, * arg;
	int opcycles = 0;
	int rx = 1, nextread = 20, interval = 40, total = 0;

	for (cycle = 1; cycle <= 220; ++cycle) {
		// Start of cycle. Do we need to read a new instruction?
		if (opcycles == 0) {
			char * toksave = NULL;

			if (!fgets(buf, sizeof(buf), stdin))
				break;

			op = strtok_r(buf, " \n", &toksave);
			arg = strtok_r(NULL, "\n", &toksave);

			// Just read instruction. Set op cycle count, and
			// perform any immediate actions
			if (strcmp(op, "noop") == 0 && !arg) {
				opcycles = 1;
			}
			else if (strcmp(op, "addx") == 0 && arg) {
				opcycles = 2;
			}
			else {
				fprintf(stderr, "Unexpected op/arg: %s/%s\n", op, arg ? arg : "(null)");
				return -1;
			}
		}

		// Mid-cycle debugger attachment.
		if (cycle >= nextread) {
			total += rx * cycle;
			nextread += interval;
		}

		// Perform cycle. Reduce opcycle count, do actions that occur on
		// op completion and increment cycle counter.
		--opcycles;

		if (opcycles == 0) {
			if (strcmp(op, "addx") == 0) {
				rx += atoi(arg);
			}
		}
	}

	printf("Sum of interesting signal strengths: %d\n", total);

	return 0;
}