TUMSO18-F: ab gift

#include <bits/stdc++.h>

using namespace std;
const int N = 1e6 + 10;
const int Const = 1e4;
using db = double;
const db INF = 1e9;
db A[N], B[N];

int main(){

    int n;
    scanf("%d", &n);

    for(int i=1;i<=n;i++){
        int a, b;
        cin >> a >> b;
        A[i] = (db) a;
        B[i] = (db) b / Const;
    }

    db mx = -INF;
    int l = 1, r = 0;
    db sum = 0.0, prod = 1.0;
    while(l <= n){
        if(sum < Const and r < n){ /// right
            r ++;
            sum += (db)(A[r] / B[r]);
            prod *= (db) B[r];
            mx = max(mx, sum * prod);
        }
        else { /// left
            sum -= (db)(A[l] / B[l]);
            prod /= (db) B[l];
            mx = max(mx, sum * prod);
            l ++;
        }
    }

    printf("%.0f", mx * Const);

    return 0;
}