// editor2
#include<stdio.h>
#include<math.h>
int main()
{
    char binary[33];
    scanf("%s",binary);
    int  n=strlen(binary);
    for( int i=0; i < n; i++)
    {
        if(binary[i] != '0' && binary[i] !='1')
        {
            printf("Invalid Input");
            return 0;
        }
    }
long long value =0;
for(int i = 0;i < n; i++)
{
    value = value*2 + (binary[i] - '0');
}
if(binary[0] == '1')
{
    value -=(1ll << n);
}
printf("%lld\n",value);
return 0;
}