Collatz solution

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

int
collatz(int n)
{
    if(n % 2 == 0){
        return n / 2;
    } else {
        return (n * 3) + 1;
    }
}

void
die(const char *msg)
{
    printf("%s\n", msg);
    exit(1);
}

int
main(int argc, char **argv)
{
    int number = 0;

    if(argc > 1){
        number = atoi(argv[1]);
    } else {
        die("Usage: ./collatz [positive integer]");
    }

    printf("%i\n", number);

    while(number > 1){
        number = collatz(number);
        printf("%i\n", number);
    }
}