#include <stdio.h>

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

	while(1){
		scanf("%c", &c);
		if(c=='\n')
			break;
		if(c>='0' && c<='9')
			c = c - '0';
		else if(c>='A' && c<='F')
			c = c-'A'+10;
		else{
			printf("-1\n");
			return 1;
		}
		s = s*16+c;
	}

	printf("%d\n", s);

	return 0;
}