#include<fstream.h>
int main()
{ifstream f("tunel.in");
 ofstream g("tunel.out");
 unsigned long n,m,x,y,c,i;
 f>>n>>m;
 unsigned long nn=0;
 for(i=1;i<=n;i++)
  {f>>x>>y>>c;
   nn+=c;
  }
f.close();
 g<<(nn/n)<<'\n';
g.close();
return 0;
}