#include <cstdio>#include <cstdlib>#include <vector>#include <algorithm>using namespace std;int main() {    int N;    double mcap, dist, davg;     scanf("%lf%lf%lf%d", &mcap, &dist, &davg, &N);    double price, idist;        vector<pair<double, double> > stations(N + 1);    for (int i=0; i<N; i++) {        scanf("%lf%lf", &price, &idist);        stations[i].first = idist;        stations[i].second= price;    }        // virtual station to indicate the end    stations[N].first = dist;    stations[N].second= 1e300;        sort(stations.begin(), stations.end());        double tank = 0, cur_dist = 0, cur_price = 0;        if (stations[0].first > 0) {        printf("The maximum travel distance = %.2lf", cur_dist);        return 0;    }        double money     = 0;        int cur_stat    = 0;    int cheap_stat     = -1;    double cheap_price = 0;        while (cur_dist < dist && (cur_stat) < N) {        double next_dist = stations[cur_stat + 1].first;        double max_dist  = mcap * davg + cur_dist;        // can‘t reach next station        if (max_dist < next_dist) {            cur_dist = max_dist;            break;        }        // can reach next station        // find first min gas price from cur_stat/cheap_stat within the reach range        if (cheap_stat < cur_stat) {            // last cheap station we calculated has past by            cheap_stat = cur_stat;            cheap_price= stations[cur_stat].second;        }        for (int i=cheap_stat; i<N && stations[i].first <= max_dist; i++) {            if (stations[i].second < cheap_price) {                cheap_stat = i;                cheap_price= stations[i].second;                break;            }        }        // cheaper station is cur_stat        if (cheap_stat == cur_stat) {            // from here we can reach end station            if (max_dist >= dist) {                money += cheap_price * (dist - cur_dist) / davg;                cur_dist = dist;                break;            }            // can‘t reach the end station            // we should fill full tank            money += (mcap - tank) * cheap_price;            tank = mcap;        } else {            // cur_stat is not the cheaper station,             // just fill enough gas, go to the cheaper one            double gas_need = (stations[cheap_stat].first - cur_dist) / davg;            if (gas_need > tank) {                // we have to fill gas here                money += (gas_need - tank) * stations[cur_stat].second;                tank = gas_need;            } else {                // we have the enough gas already            }                    }        // now we have enough gas        // drive to the next station        tank -= (next_dist - cur_dist) / davg;        cur_stat++;        cur_dist = next_dist;    }    if (cur_dist < dist) {        printf("The maximum travel distance = %.2lf", cur_dist);    } else {        printf("%.2lf", money);    }    return 0;}