POJ_1730_Perfect Pth Powers

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

const double eps = 1e-12;

int main(){

double n;

while( 1 ){

cin >> n;

if( n == 0 )
break;

if( n > 0 ){
for( int i = 31; i >= 1; --i ){

double sum = pow( n, 1.0 / i );
double up = ceil( sum );
double down = floor( sum );

if( fabs( up - sum ) < eps || fabs( sum - down ) < eps ){
cout << i << endl;
break;
}
}
}
else{

n = -n;

for( int i = 31; i >= 1; i -= 2 ){

double sum = pow( n, 1.0 / i );
double up = ceil( sum );
double down = floor( sum );

if( fabs( up - sum ) < eps || fabs( down - sum ) < eps ){
cout << i << endl;
break;
}
}
}
}

return 0;
}