#include<stdio.h>
#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\n");
            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;
}