// editor2
#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');
    }
    printf("%d\n", decimal);
    return 0;
}