题目：给出表面积n，求长宽高，如果无解，输出Impossible!

我的SPJ：

#include "testlib.h"
#include <bits/stdc++.h>
using namespace std;
int to_int(string a)
{
	int j = 0;
	int ans = 0;
	for (int i = a.size() - 1; i >= 0; i --)
	{
		ans += (a[i] - '0') * (pow(10, j));
		j ++;
	}
	return ans;
}
int main(int argc, char* argv[])
{
    registerTestlibCmd(argc, argv);
    string aa = ouf.readString();
    string nn = ans.readString();
    if (aa == "Impossible!" && nn == "Impossible!")
	{
		quitf(_ok, "The answer is correct.");
		return 0; 
	} 
    int b = ouf.readInt();
    int h = ouf.readInt();
	int n = to_int(nn);
	int a = to_int(aa);
    if (2 * (a * b + a * h + b * h) == n)
        quitf(_ok, "The answer is correct.");
    else
        quitf(_wa, "The answer is wrong. 2 * (%d * %d + %d * %d + %d * %d) != %d", a, b, a, h, b, h, n);
}

结果错了，求调。