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