#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;
}