poj 2719 Faulty Odometer

#include<stdio.h>#include<string.h>#include<math.h>#define POW (int)pow(10.0,(len-i-1)*1.0)int main(){int s[10]={0,9,81,729,6561,59049,531441,4782969,43046721,387420489};char num[20];int len,i,ans,m;while(scanf("%s",num)!=EOF){if(strcmp(num,"0")==0)break;ans=m=0;len=strlen(num);for(i=0;i<len;i++)m=m*10+num[i]-'0';for(i=0;i<len-1;i++){if(num[i]>'4')num[i]=num[i]-1;ans+=s[len-i-1]*(num[i]-'0');}if(num[i]>='4')num[i]--;ans+=(num[i]-'0');printf("%d: %dn",m,ans);}return 0;}