Careful Ascent Solution:

#include <bits/stdc++.h>
using namespace std;

int main(){
    // #ifndef TESTING
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    // #endif
    
    int x, y, nShields;
    double shieldSum = 0;
    cin >> x >> y >> nShields;
    while(nShields--){
        double start, end, multiplier;
        cin >> start >> end >> multiplier;
        shieldSum += multiplier * (end - start);
        y -= end - start;
    }
    cout << fixed << setprecision(7);
    cout << x / (shieldSum + y) << endl;
    return 0;   
}