static class FenwickTree {
        private long[] tree;
        private int size;

        public FenwickTree(int size) {
            this.size = size;
            tree = new long[size + 1];
        }

        public void update(int idx, long val) {
            while (idx <= size) {
                tree[idx] += val;
                idx += idx & -idx;
            }
        }

        public long query(int idx) {
            long result = 0;
            while (idx > 0) {
                result += tree[idx];
                idx -= idx & -idx;
            }
            return result;
        }
    }

    static class Dividend {
        public long amount = 0;
        public long days = 0;

        public Dividend(long amount, long days) {
            this.amount = amount;
            this.days = days;
        }
    }

    static class FuturePricingEngine {
        private long stockPrice;
        private List<Dividend> dividends;
        private FenwickTree fenwickTree;

        public FuturePricingEngine(long stockPrice, List<Dividend> dividends) {
            this.stockPrice = stockPrice;
            this.dividends = dividends;
            int maxDays = (int) dividends.stream().mapToLong(dividend -> dividend.days).max().orElse(0);
            fenwickTree = new FenwickTree(maxDays);
            for (Dividend dividend : dividends) {
                fenwickTree.update((int) dividend.days, dividend.amount);
            }
        }

        public void updateDividend(int dividendIndex, Dividend updatedDividend) {
            dividendIndex -= 1;
            Dividend oldDividend = dividends.get(dividendIndex);
            fenwickTree.update((int) oldDividend.days, -oldDividend.amount);
            fenwickTree.update((int) updatedDividend.days, updatedDividend.amount);
            dividends.set(dividendIndex, updatedDividend);
        }

        public long calculateFuturePrice(long daysToFuture) {
            long totalDividends = fenwickTree.query((int) daysToFuture);
            return stockPrice - totalDividends;
        }
    }