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