#include<stdio.h>
#include<string.h>
int main() {
    char s[33];
    scanf("%s", &s);
    long long d = 0;
    int l = strlen(s);
    for (int i = 0; i < l; i++){
        if (s[i] != '0' && s[i] != '1') {
            printf("Invalid input\n");
            return 1;
        }
        if (s[i] == '1') d += (i == 0) ?- (1LL << (l - 1)) : (1LL << (l - 1 - i));
    }
    printf("%lld\n", d);
    return 0;
}