collatz conjecture

collatz_conjecture.cpp

#include <stdio.h>
#include <limits.h>    
const int s = 30;

bool f(long i)
{
    int r = 0;
    for(;;)
        if (i < 0 || r > s) return false;
        else if (i == 1) break;
        else{r ++;i = i % 2 ? 3*i + 1 : i/2;}
    return (r==s);
}

int main(){
    for(long i = 1; i < LONG_MAX; i++) if (f(i)) printf("%ld ", i);
    return 0;
}