// editor2#include <stdio.h>
#include <string.h>
#include <math.h>

int binaryToTwosComplementDecimal(char *bin) {
    int n = strlen(bin);  // length of binary string
    int decimal = 0;

    // Check if MSB is 1 → negative number in two's complement
    if (bin[0] == '1') {
        // Convert normally first
        for (int i = 0; i < n; i++) {
            if (bin[i] == '1') {
                decimal += (1 << (n - i - 1));
            }
        }
        // Apply two's complement rule: subtract 2^n
        decimal -= (1 << n);
    } else {
        // Positive number → normal binary to decimal
        for (int i = 0; i < n; i++) {
            if (bin[i] == '1') {
                decimal += (1 << (n - i - 1));
            }
        }
    }

    return decimal;
}

int main() {
    char bin[65];  // Support up to 64-bit binary

    printf("Enter a binary string: ");
    scanf("%s", bin);

    int result = binaryToTwosComplementDecimal(bin);

    printf("Decimal value (two's complement) = %d\n", result);

    return 0;
}