求纯手工计算方法，我计算不下去了。

#include <stdio.h>
void main()
{
    int a, n;//计算a的开n次方
    double low, high, middle, x;

    scanf("%d%d", &a, &n);

    int i, j, tmp;

    for (i=1; i<a; i++)
    {
        tmp = 1;
        for (j=0; j<n; j++)
        {
            tmp *= i;
        }
        if (tmp >= a)
        {
            break;
        }
    }

    low = i - 1;
    high = i;

    while (1)
    {
        middle = (low+high)/2;

        x = 1;
        for (j=0; j<n; j++)
        {
            x *= middle;
        }
        if (x - a < 0.0001 && x - a > -0.0001)
        {
            printf("%lf\n", middle);
            break;
        }
        if (x > a)
        {
            high = middle;
        }
        else
        {
            low = middle;
        }
    }
}