#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
uint16_t result = 0;
uint8_t i = 0;
while(str[i] != '\0'){
i++;
}
uint8_t v = i-1;
for(int j = 0; j < i; j++){
uint8_t ram = str[j] - '0';
result += (1 << v) * ram;
v--;
}
return result;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}