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

typedef unsigned int uint32;
typedef unsigned long long uint64;

uint64 nearest_power_of_2(uint32 n);

int main(int argc, char* argv[])
{
    if (argc < 2) {
        printf("usage %s integer\n", argv[0]);
        return -1;
    }

    uint32 n = atoi(argv[1]);

    printf("Input: %u\nNearest power of 2: %llu\n", n,
        nearest_power_of_2(n));

    return 0;
}

uint64
nearest_power_of_2(uint32 n)
{
    uint32 i;

    if (n == 0)
        return 0;

    for (i = 31; i > 0; i--) {
        if (n > (1UL << i))
            return 1UL << (i + 1);
    }

    return n;
}