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

//加油站
struct Station{
	double price;//单位油价
	double dist;//该加油站距离杭州距离
};

//最后输出打印
struct Print{
	int flag;//是否到达
	double pri;//若到达此处为how much；若未到达此处为how far has run
};

//按照距离杭州最近的排序
bool cmpD(Station a, Station b){
	return a.dist <= b.dist;
}

//cmax邮箱最大油；davg单位油可跑的距离；num加油站数量；D到目的城市的总距离
Print Loop(int cmax, int davg, int num, double D){
	Print result;
	Station gas[num+1];
	//将单位油价格，转为单位距离价格
	for(int i=0; i<num; i++){
		double unitPri;
		cin >> unitPri >> gas[i].dist;
		gas[i].price = unitPri / davg;
	}
	//按距离排序
	sort(gas, gas+num, cmpD);
	
	double run_max = cmax * davg * 1.0;//油箱满油最多可跑的距离
	double run_fina = 0.0;//共跑了多少距离
	double run_left = 0.0;//跑到加油站后还能再跑多少距离
	double ival;//两个加油站之间的距离
	double pri_fina = 0.0;//最终价格
	double pri_now = 9999.0;//现在的加油站的价格；初始设置为一大值，后面都会进行赋值覆盖
	gas[num].dist = D;//总距离
	for(int i=0; i<num; i++){
		ival = gas[i+1].dist - gas[i].dist;
		//无法...