HDU 4278 Faulty Odometer

#include <stdio.h>
#include <string.h>
int main()
{
long a[10]={0,1,2,0,3,4,5,6,0,7},i,j,sum,k;
char s[100];
while(~scanf("%s",&s)){
if(strcmp(s,"0")==0) break;
sum=0;k=1;
for(i=strlen(s)-1;i>=0;i--)
{
sum+=a[s[i]-'0']*k;
k*=8;
}
printf("%s: %ld\n",s,sum);
}
}