#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <math.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
int l = strlen(str);
uint16_t num = 0;
for(int x=l-1;x>=0;x--)
{
num += (str[x] - '0')*(int)pow(2,l-1-x);
}
return num;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}