#include<bits/stdc++.h>

const double eps=1.0e-9;

using namespace std;
using pi=pair<int,int>;
using pdpi=pair<double,pi>;

int main(){
  int x,y;
  cin >> x >> y;
  x--;y--;
  int rd=x*600+y;

  int n;
  cin >> n;
  vector<int> sx(n),sy(n),sv(n);
  double dp[393939][16];
  for(int i=0;i<393939;i++){
    for(int j=0;j<16;j++){
      dp[i][j]=1.0e9;
    }
  }
  double len[32];
  for(int i=1;i<32;i++){len[i]=1000.0/((double)i);}

  priority_queue<pdpi,vector<pdpi>,greater<pdpi>> pq;
  for(int i=0;i<n;i++){
    cin >> sx[i] >> sy[i] >> sv[i];
    sx[i]--;sy[i]--;
    if(i){
      dp[sx[i]*600+sy[i]][sv[i]]=0.0;
      pq.push({0.0,{sx[i]*600+sy[i],sv[i]}});
    }
    else{
      dp[sx[i]*600+sy[i]][7+sv[i]]=0.0;
      pq.push({0.0,{sx[i]*600+sy[i],7+sv[i]}});
    }
  }

  while(!pq.empty()){
    pdpi od=pq.top();pq.pop();
    int vp=od.second.first;
    int vt=od.second.second;
    if(dp[vp][vt]<od.first){continue;}
    //cout << od.first << ':';
    //cout << vp << ' ';
    //cout << vt << '\n';
    if(od.second.first==rd && vt>=8){
      printf("%.12lf\n",od.first);
      return 0;
    }
    vector<int> kh;
    if(vp%600!=0){kh.push_back(vp-1);}
    if(vp%600!=599){kh.push_back(vp+1);}
    if((vp-600)>=0){kh.push_back(vp-600);}
    if((vp+600)<360000){kh.push_back(vp+600);}
    if(vt<=7){
      for(auto &nx : kh){
        if(dp[nx][vt]>od.first+len[vt]){
          dp[nx][vt]=od.first+len[vt];
          pq.push({od.first+len[vt],{nx,vt}});
        }
        for(int i=8;i<=14;i++){
          if(i-7>=vt){continue;}
          if(dp[nx][i]>od.first+eps){continue;}
          int nv=7+max(vt,i-7);
          if(dp[nx][i]+len[i-7]+eps>=od.first){
            double reml=max(0.0,1000.0-(od.first-dp[nx][i])*(i-7.0));
            double kgl=reml*vt/(i+vt-7.0);
            double kgt=reml/(i+vt-7.0);
            //cout << reml << ' ' << kgl << ',' << kgt << '\n';
            int tg=vp;
            double nt=od.first+2.0*kgt;
            if(dp[tg][nv]>nt){
              dp[tg][nv]=nt;
              pq.push({nt,{tg,nv}});
            }
            tg=nx;
            nt=od.first+kgt+(1000.0-kgl)/(nv-7.0);
            if(dp[tg][nv]>nt){
              dp[tg][nv]=nt;
              pq.push({nt,{tg,nv}});
            }
          }
        }
      }
    }
    else{
      for(auto &nx : kh){
        if(dp[nx][vt]>od.first+len[vt-7]){
          dp[nx][vt]=od.first+len[vt-7];
          pq.push({od.first+len[vt-7],{nx,vt}});
        }
        for(int i=1;i<=7;i++){
          if(vt-7>=i){continue;}
          if(dp[nx][i]>od.first+eps){continue;}
          int nv=7+max(vt-7,i);
          if(dp[nx][i]+len[i]+eps>=od.first){
            double reml=max(0.0,1000.0-(od.first-dp[nx][i])*((double)i));
            double kgl=reml*(vt-7.0)/(i+vt-7.0);
            double kgt=reml/(i+vt-7.0);
            //cout << reml << ' ' << kgl << '@' << kgt << '\n';
            int tg=vp;
            double nt=od.first+2.0*kgt;
            if(dp[tg][nv]>nt){
              dp[tg][nv]=nt;
              pq.push({nt,{tg,nv}});
            }
            tg=nx;
            nt=od.first+kgt+(1000.0-kgl)/(nv-7.0);
            if(dp[tg][nv]>nt){
              dp[tg][nv]=nt;
              pq.push({nt,{tg,nv}});
            }
          }
        }
      }
    }
  }
  return 0;
}