#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("%11d\n",decimal_val);
}
int main()
{
    solve ();
    return 0;
}