#include<stdio.h>
int main()
{
    char binaryInput[32];
    long long decimalEquivalent=0;
    long long base=1;
    int remainder;
    scanf("%s", binaryInput);
    while (binaryInput>0)
    {
        remainder = binaryInput % 10;
        decimalEquivalent += remainder * base;
        binaryInput /= 10;
        base *= 2;
    }
    printf("%lld", decimalEquivalent);
    return 0;
}