float fitness() {
    // calcular las distancias
    float dist = 0;
    for ( unsigned i = 0; i < FILESIZE; i ++ ) {
	for (unsigned j = 0; j < 2; j ++ ) {
	    float distk = (__sample[i][j] - __gen[j]);
	    dist += distk*distk;
	}
	dist += sqrt( dist );
    }
    return 1/dist;
}