#include <stdio.h>

int main(){
	int v = 0;
	char c;

	scanf("%c", &c);
	while(c!='\n'){
		if(c>='0' && c<='1')
			v = v*2+c-'0';
		else{
			printf("-1\n");
			return 1;
		}
		scanf("%c", &c);
	}
	
	printf("%d\n", v);

	return 0;
}