#include <stdio.h>
#include <string.h>
#include <stdlib.h.
int main(){
    char binary[33];
    scanf("%32s", binary);
    for(int i = 0; i <strlen(binary); i++){
        if(binary[i] != '0' && binary[i] != '1') {
            printf("Invalid Input\n");
            return 0;
        }
    }
    int len = strlen(binary);
    int decimal = 0;
    if(binary[0] == '1') {
        decimal = -((1 << len) - strtol(binary, NULL, 2));
    }else{
        decimal = strtol(binary, NULL, 2);
    }
    printf("%d\n",decimal);
    return 0;
}