#include<iostream>
#include<string>
using namespace std;

const int size=1000010;
char a[size];
int b[size],c[size];
int main ()
{
    int len;
    __int64 count=1;
    while (cin>>a)
    {
          len=strlen(a);
          int j=0;
          for (int i=len-1;i>=0;i--)
              b[j++]=a[i]-'0';
          c[0]=b[0];
          b[len]=1; 
          for (int i=1;i<len;i++)
          {
              if (b[i]<c[i-1])
              {
                  b[i]=b[i]+10;
                  b[i+1]=b[i+1]-1;              
              }
              c[i]=b[i]-c[i-1];  
          }   
    if (c[len-1]==0)
    printf("%lld. IMPOSSIBLE\n",count++);
    else
    {
        printf("%lld. ",count++); 
        for (int i=len-1;i>=0;i--)
            printf("%d",c[i]);
        printf("\n");
    }
    }
    return 0;   
} 

但在poj上交去总是wa，找不出原因。困惑！！！

不是意思我弄错了，应该是Compile Error
他的提示是：
Main.cc: In function 'int main()':
Main.cc:14: error: 'strlen' was not declared in this scope
Main.cc:30: error: 'printf' was not declared in this scope
Main.cc:33: error: 'printf' was not declared in this scope
按你那样改过来还是不对

用的是G++的编译器