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