#include<string.h>
int main()
{
    char binary[33];
    int i, decimal = 0;
    scanf("%s",binary);
    int len = strlen(binary);
    for (i = 0; i < len; i++)
    {
        if (binary[i] != '0' && binary[i] !='1')
        {
            printf("Invalid Input");
            return 0;
        }
    }
    for (i = 0; i < len; i++)
    {
        decimal = decimal * 2 + (binary[i] - '0');
    }
    if (binary[0] == '1')
    {
        decimal = decimal - (1 << len);
    }
    printf("%d\n",decimal);
    return 0;
}