problem：T139852

code:

#include <bits/stdc++.h>
#define R register
#define inl inline
#define fastios ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
#define Debug(file) freopen(file".in","r",stdin);freopen(file".out","w",stdout);
using namespace std;

template<typename T> inline void read(T &x) {
	char In[1 << 20], *ss = In, *tt = In;
	x = 0;
	char q;
	bool f = 1;
	while (!isdigit(q = getchar()))
		if (q == '-')
			f = 0;
	while (isdigit(q)) {
		x = (x << 1) + (x << 3) + (q ^ 48);
		q = getchar();
	}
	x = f ? x : -x;
}

template<typename T> inline void write(T x) {
	if (x < 0) {
		putchar('-');
		x = -x;
	}
	if (x > 9)
		write(x / 10);
	putchar(x % 10 + '0');
}

int main() {
#define int long long
	int n, step(0);
	read(n);
	while (n != 1) {
		switch (n % 3) {
			case 0:
				n /= 3;
				break;
			case 1:
				n--;
				break;
			case 2:
				n++;
		}
		step++;
	}
	write(step), putchar('\n');
	return 0;
}

萌新在此谢过大佬们了！