#include <stdio.h>
#include <string.h>
int main() {
        char binary[33];
        int i, decimal = 0;
        
        scanf("%s", binary);
        int len = strlen(binary);
        for ( i=0;i<len;i++){
            if (binary[i]!='0' && binary [i] !='1'){
                printf("Invalid Input\n");
                return 0;
            }
        }
        for (i=0;i<len;i++){
            decimal = decimal * 2 + ( binary[i]) - '0');
        }
        if (binary[0] =='1'){
            decimal = decimal - (1<<len);
        }
        
        printf("%d\n", decimal);
        return 0;
}