A. Secrets
http://codeforces.com/problemset/problem/333/A
time limit per test
memory limit per test
input
output
n
One day an unlucky buyer came. He did not have the desired sum without change. Then he took out all his coins and tried to give Gerald a larger than necessary sum with as few coins as possible. What is the maximum number of coins he could get?
The formal explanation of the previous paragraph: we consider all the possible combinations of coins for which the buyer can not give Gerald the sum of n marks without change. For each such combination calculate the minimum number of coins that can bring the buyer at least n
Input
n (1 ≤ n ≤ 1017).
%lld specifier to read or write 64 bit integers in С++. It is preferred to use the cin, cout streams or the %I64dspecifier.
Output
In a single line print an integer: the maximum number of coins the unlucky buyer could have paid with.
Sample test(s)
input
1
output
1
input
4
output
2
题目是这个意思：
让面额总数大于n而又最接近n，且所用硬币总数还最多。
首先1分不能用，假设可以用，则有1+x>n，所以x>=n，如果x=n，则不符合题意，所以x>n，这说明x就能满足要求，所以1分是不能用的。
同理可以证明，当n=3k时，3分是不能用的；当n=9k时，9分是不能用的；……
所以判断n最多是3的多少次方的倍数就行。
完整代码：
/*30ms,0KB*/
#include<cstdio>
int main(void)
{
__int64 n, deno = 3; //denomination
scanf("%I64d", &n);
for (; n % deno == 0; deno *= 3)
;
printf("%I64d", n / deno + 1);
return 0;
}
