#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("Invlaid 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;
}