#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include <string.h>
uint16_t binary_to_uint(const char *str) {
uint8_t index_counter = 0;
uint16_t num = 0x0;
for(uint8_t i=strlen(str); str[i]>=0; i--)
{
if(str[i]=='1' || str[i]=='0')
{
if(str[i]=='1')
{
num+= 1 * (pow(2,index_counter));
}
index_counter++;
}
}
return num;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}