#ifdef __FAST_MATH__
#undef __FAST_MATH__
#endif

#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <inttypes.h>
#include <queue>

struct region_t
 {
  double start;
  double end;
  double z;
  
  region_t( double const& s=0, double const& e=0, double const& z=0 ) : start(s), end(e), z(z) {}
 };

bool operator < ( struct region_t const& a, struct region_t const& b )
 {
  if( a.z < b.z )
    return true;
  return false;
 }

region_t project_tree( int x_i, int y_i, int r_i )
 {
  double       x = x_i;
  double       y = y_i;
  double const l = sqrt( x*x + y*y );
  double const r = r_i;
  double const a = asin( r/l );
  
  x /= l;
  y /= l;
  
  double phi = acos( y );
  if( asin(x) < 0 )
    phi += 2.0*(M_PI-phi);
    
  region_t reg( phi-a, phi+a, l-r );
  //if( reg.start < 0 ) reg.start += 2.0*M_PI;
  //if( reg.end < 0 )   reg.end   += 2.0*M_PI;
  return reg;
 }

std::vector<region_t> regions;

void recalculate_visible_areas( void )
 {
  for( std::vector<region_t>::iterator i = regions.begin(); i != regions.end(); ++i )
    for( std::vector<region_t>::iterator j = i+1; j != regions.end(); ++j )
     {
      if( j->z < i->z )
        continue;
      
      bool const shift_i = i->start < 0;
      bool const shift_j = j->start < 0;
      
      if( shift_i ) { i->start += 2.0*M_PI; i->end += 2.0*M_PI; }
      if( shift_j ) { j->start += 2.0*M_PI; j->end += 2.0*M_PI; }

      if( i->start <= j->start && i->end >= j->end ) /// komplett verdeckt
        j->z = 0;
      else if( i->end > j->start && i->end < j->end ) /// 'links' verdeckt
        j->start = i->end;
      else if( i->start > j->start && i->start <= j->end ) /// 'rechts' verdeckt
        j->end = i->start;
      else /// verdeckt ueberhauptnicht.
        {}
      
      if( shift_i ) { i->start -= 2.0*M_PI; i->end -= 2.0*M_PI; }
      if( shift_j ) { j->start -= 2.0*M_PI; j->end -= 2.0*M_PI; }
     }
 }

int main( int argsc __attribute__((unused)), char ** argsv __attribute__((unused)) )
 {
  int      i,n;
  int      x,y,r;
  FILE    *input = fopen("forest.in", "rt");
  regions.resize(1000);
  
  assert( input && "file \'forest.in\' not in working directory" );
  
  while( fscanf( input, "%d", &n ) == 1 )
   {
    if( !n )
      break;
    
    for( i=0; i<n; ++i )
     {
      fscanf( input, "%d %d %d", &x, &y, &r );
      regions[i] = project_tree( x, y, r );
     }
    std::sort( &regions[0], &regions[n] );
    recalculate_visible_areas();
    std::sort( &regions[0], &regions[n] );
    /*for(i=0;i<n;++i)
      printf( "%.3lf,%.3lf,%.3lf\n", regions[i].start, regions[i].end, regions[i].z );*/
    printf("%.3f\n", regions[n-1].z);
   }
  
  fclose( input );
  return EXIT_SUCCESS;
 }