Quad igual a Soma

#include <stdio.h>

int _val(int num, int inf, int max);
int _Quad(float num, int x);
int _Lenght(int num);

int main()
{
    int Input, first, second, temp;
    int tamanho, count, resto;
    int max_cicle, min_cicle;
    int n;
    first = second = tamanho = temp = count = resto = min_cicle = 0;
    n = 0;
    printf("Introduza um Numero par inteiro entre 2 e 8: ");
    scanf("%d", &Input);
    if( ( !_val(Input, 2, 8) && (Input % 2 == 0) ) )
    {
        printf("\n ERRO \n");
        return 0;
    }

    switch(Input)
    {
    case 2: max_cicle = 99; break;
    case 4: max_cicle = 9999; break;
    case 6: max_cicle = 999999; break;
    case 8: max_cicle = 99999999; break;
    }

    tamanho = Input;
    for(;n <= max_cicle;n++)
    {
        if( Input == 2)
        {
            first = n / 10;
            second = n % 10;
        }
        else    if( Input == 4)
        {
            first = n / 100;
            second = n % 100;
        }
        else    if( Input == 6)
        {
            first = n / 1000;
            second = n % 1000;
        }
        else    if( Input == 8)
        {
            first = n / 10000;
            second = n % 10000;
        }

        if( _Quad((first + second), 2) == n )
            printf("\n %d", n);
    }

    printf("\n\n");
    return 0;
}

int _val(int num, int inf, int max)
{
    return (num >= inf && num <= max) ? 1 : 0;
}

int _Quad(float num, int x)
{
    int temp = 1;
    while(x!=0)
    {
        temp*=num;
        x--;
    }
    return temp;
}
int _Lenght(int num)
{
    int resto, x;
    resto = x = 0;
    while( num > 0 )
    {
        resto = num % 10;
        num /= 10;
        x++
    }
    return x;
}