为什么编译器在此代码中说POW(N，K）含糊不清

在xcode 4.5（Mac）下编译以下代码时，汇编失败，以下错误消息：

call to 'pow' is ambiguous

为什么？谢谢！

#include <iostream>
#include <cmath>
#include <limits>
using namespace std;
int main()
{
    cout << "tSquare root calculator using an emulation the ENIAC's algorithm." << endl
         << endl;
    long long m;
    while ((cout << "Enter a positive integer:" << endl)
            && (!(cin >> m) || m < 0 || m > 9999999999)) //10-digit maxium
    {
        cout << "Out of range.";
        cin.clear();
        cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
    }
    again:
    long long l = m;
//Find out how big the integer is and adjust k accordingly.
    int order = -1;
    long long temp = m;
    do
    {
        temp /= 10;
        order++;
    } while (temp/10);
    int k = order/2;
//Step 1
    long long a = -1;
    do
    {
        a+=2;
        m -= a*pow(100,k);
    } while (m >= 0);
    while (k > 0)
    {
        k--;
//Step 2
        if (m < 0)
        {
            a = 10*a+9;
            for (;m < 0;a -= 2)
            {
                m += a*pow(100,k);
            }
            a += 2;
        }
//Step 3
        else
        {
            a = 10*a-9;
            for(;m >= 0;a += 2)
            {
                m -= a*pow(100,k);
            }
                 a -= 2;
        }
    }
//Step 4
    cout << endl << "The square root of " << l << " is greater than or equal to "
         << (a-1)/2 << " and less than " << (a+1)/2 << "." << endl << endl;
    while ((cout << "Enter a positive integer to calculate again, or zero to exit." << endl)
            && (!(cin >> m) || m < 0 || m > 9999999999))
    {
        cout << "Out of range.";
        cin.clear();
        cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
    }

    if (m > 0) goto again;
    return 0;
}