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