#pragma GCC optimize("Ofast")
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
#include <deque>
#include <stack>
#include <sstream>
#include <utility>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n,r,m; cin >> n >> r >> m;

    int rem=r-n; // rem未満のロスならok
    vector<int> t(m+2);
    vector<double> p(m+2);
    vector<int> d(m+2);
    for(int i=0;i<m;i++){
        cin >> t[i+1] >> p[i+1] >> d[i+1];
    }
    t[0]=0; t.back() = n;
    p[0]=1.0; p.back() = 1.0;
    d[0]=0; d.back() = 0;

    double L=0,R=1e9;
    vector<vector<double>> dp(m+2,vector<double>(rem));
    for(int _=0;_<200;_++){
        double mid=(L+R)/2.0;
        for(int i=m;i>=0;i--){
            for(int j=rem-1;j>=0;j--){
                dp[i][j] = p[i] * (t[i+1]-t[i]+dp[i+1][j]);
                if(j+d[i]>=rem)dp[i][j] += (1-p[i]) * mid;
                else dp[i][j] += (1-p[i]) * min(mid, t[i+1]-t[i]+d[i]+dp[i+1][j+d[i]]);
            }
        }
        if(dp[0][0] > mid) L = mid;
        else R = mid;
    }
    printf("%.9f\n",L);
}