#include<stdio.h>
int main()
{
    int n;
    int count=0;
    scanf("%d",&n);
    while(n!=0)

    {

        n=n%10;
        if(n==4 || n==7)
            count++;

    }

    if(count==4 || count==7)
        printf("YES");
    else
        printf("N0");









    return 0;
}