Codeforces Burning Midnight Oil

/*
 * BurningMidnightOil.cpp
 *
 *  Created on: 2013-10-12
 *      Author: wangzhu
 */

/**
 * 每次至少写多少行代码ret：
 * 1)、当n<=k时，肯定是ret = n;
 * 2）、当n > k时，则 ret>=k&ret <= n，故只需要按二分的思路将其查找一下，就可以，
 * 对于每一个可能的值进行计算可以书写的代码行，之后继续，最后得到的结果就是答案
 */
#include<cstdio>
#include<iostream>
using namespace std;
#define LL long long
LL calc(int k, int v) {
    //数据容易溢出
    LL sum = v, kk = k;
    while (v / kk) {
        sum += v / kk;
        kk *= k;
    }
    return sum;
}
int binarySearch(int n, int k) {
    LL left = k, right = n, mid = -1;
    while (left <= right) {
        mid = left + (right - left) / 2;
        if (n <= calc(k, mid)) {
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    return (int) left;
}
int main() {
    freopen("data.in", "r", stdin);
    int n, k;
    while (~scanf("%d%d", &n, &k)) {
        if(n <= k) {
            printf("%d
",n);
            continue;
        }

        printf("%d
", binarySearch(n, k));
    }
    return 0;
}