zoj 1712 Skew Binary

#include <iostream>#include <stdio.h>#include <string.h>#include <math.h>using namespace std;int main(){    int i;    double l,sum;    char s[31];    while(gets(s)&&strcmp(s,"0") != 0)    {       l=strlen(s);       sum=0;       for(i=0;i<strlen(s);i++,l--)          sum=sum+(s[i]-'0')*(pow(2,l)-1);       cout<<int(sum)<<endl;    }        return 0;}