# B类
# 题目链接：
https://abc114.contest.atcoder.jp/tasks/abc114_c
# 原题：
**Problem Statement**
You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?
Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:
- When the number is written in base ten, each of the digits '7', '5' and '3' appears at least once, and the other digits never appear.
**Constraints**
- 1≤N<1e9
- N is an integer.
**Input**
Input is given from Standard Input in the following format:
N
**Output**
Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).
------------
**Sample Input 1**
575
**Sample Output 1**
4
There are four Shichi-Go-San numbers not greater than 575: 357,375,537 and 573.
------------
**Sample Input 2**
3600
**Sample Output 2**
13
There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735,753,3357,3375,3537,3557,3573,3575 and 3577.
------------
**Sample Input 3**
999999999
**Sample Output 3**
26484
# 题意：
从1到N，有多少个“七五三”数,“七五三”数是这样规定的：数字中只有7,5和3，且至少全部都有一个。
# 思路：
### （刚开始看成数学题了，导致自闭做不出来
### (别说了，又是赛后过题o(╥﹏╥)o
深搜把所有的3,5,7存下来，当3,5,7全部都有以上时，答案数就加一，注意开long long
# AC代码：
```
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
using namespace std;
#include<algorithm>
#include<queue>
typedef long long ll;
#include<vector>
#include<set>
#define cin(n) scanf("%lld",&(n))
#define cout(n) printf("%lld",(n))
#define couc(c) printf("%c",(c))
#define coutn printf("\n")
#define cout_ printf(" ")
set<int> s;
const int MAXN= 1e4 + 5 ;
ll n;
ll ans;
void dfs(ll l,ll a,ll b,ll c)
{
if(l>n) return;
if(a>=1&&b>=1&&c>=1) ans++;
dfs(l*10+3,a+1,b,c);
dfs(l*10+5,a,b+1,c);
dfs(l*10+7,a,b,c+1);
}
int main()
{
scanf("%lld",&n);
dfs(0,0,0,0);
printf("%lld",ans);
return 0;
}
```