#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

// mmap
#include <sys/mman.h>
// write
#include <unistd.h>
// exit
#include <stdio.h>
#include <stdlib.h>

int main() {
    unsigned long long x;
    (void)scanf("%lld", &x);

    for (int m = 0; m < 64; ++m) {
        unsigned long long n = x ^ m;
        if (n <= 0) continue;
        int m2 = __builtin_popcountll(n);
        if (m2 == m) {
            printf("%lld\n", n);
            return 0;
        }
    }

    printf("-1\n");
    exit(0);
    return 0;
}