Nearly Lucky Number

最新推荐文章于 2021-12-09 08:50:25 发布

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本文介绍了一个算法，用于判断一个数是否为近乎幸运数。近乎幸运数是指该数中包含的幸运数字（4和7）的数量本身也是一个幸运数。文章通过示例详细解释了算法的工作原理，并提供了完整的代码实现。

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Nearly Lucky Number
Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Unfortunately, not all numbers are lucky. Petya calls a number nearly lucky if the number of lucky digits in it is a lucky number. He wonders whether number n is a nearly lucky number.

Input

The only line contains an integer n (1 ≤ n ≤ 1018).

Please do not use the %lld specificator to read or write 64-bit numbers in С++. It is preferred to use the cin, cout streams or the %I64d specificator.

Output

Print on the single line "YES" if n is a nearly lucky number. Otherwise, print "NO" (without the quotes).

Examples
Input

40047

Output

NO

Input

7747774

Output

YES

Input

1000000000000000000

Output

NO

Note

In the first sample there are 3 lucky digits (first one and last two), so the answer is "NO".

In the second sample there are 7 lucky digits, 7 is lucky number, so the answer is "YES".

In the third sample there are no lucky digits, so the answer is "NO".

问题分析：
此程序需要注意判断的是近乎幸运的数字，是包含7或4的数字中，有7个或4个的数字为近乎幸运的数字。

#include<iostream>
#include<cstring>
using namespace std;
char a[1000];int i;
int main()
{
	
	cin>>a;
	int sum=0;
	int len=strlen(a);
	for(i=0;i<len;i++)
	{
	
		if(a[i]=='4'||a[i]=='7')
		sum++;
		
	}
	if(sum==4||sum==7)
	cout<<"YES"<<endl;
	else cout<<"NO"<<endl;
	
}