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

int main(void) {
    FILE *fp = fopen("input.txt", "r");
    char buf[16];
    unsigned rlen = sizeof(buf) - 1;
    unsigned bitcnt[2][sizeof(buf) - 1] = {0};
    size_t gamma = 0, epsilon = 0;

    while (fgets(buf, sizeof(buf), fp) != NULL) {
        for (size_t i = 0; i < rlen; i++) {
            if (buf[i] == '0')
                bitcnt[0][i]++;
            else if (buf[i] == '1')
                bitcnt[1][i]++;
            else {
                rlen = i;
                break;
            }
        }
    }

    for (size_t i = 0; i < rlen; i++) {
        if (bitcnt[0][i] < bitcnt[1][i])
            gamma ^= 1 << (rlen - i - 1);
        else
            epsilon ^= 1 << (rlen - i - 1);
    }

    printf("Answer: %lu\n", gamma * epsilon);
}