TUMSO18: AB Gift

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

const int N = 1e6;

int arrA[N + 1];
double arrB[N + 1];

int main(){

    int nItems;
    scanf("%d", &nItems);
    arrB[0] = 1;
    for(int i = 1; i <= nItems; ++i){
        int bVal;
        scanf("%d%lf", &arrA[i], &arrB[i]);
        arrB[i] /= 1e4;
    }
    int j = 0;
    double mx = 0;
    double sum = 0;
    double product = 1;
    for(int i = 1; i <= nItems; ++i){
        while(j < nItems && sum < 1e4){
            sum += arrA[j + 1] / arrB[j + 1];
            product *= arrB[j + 1];
            ++j;
        }
        mx = max(mx, sum * product);
        sum -= arrA[i - 1] / arrB[i - 1];
        product /= arrB[i - 1];
    }
    printf("%.0f", mx * 1e4);

    return 0;
}