110 A.cpp

/**
* Git >> Mohsin_Riad

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**/
#include<bits/stdc++.h>
using namespace std;

#define IOS ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define mx 1000
#define endl "\n"
#define pb push_back
#define pob pop_back
typedef long long ll;
typedef double dd;
const int N = 1e6;

ll n;

int calc(ll x)
{
    ll cnt1 = 0, cnt2 = 0, cnt3 = 0;
    while(x!=0)
    {
        cnt1++;
        ll temp = x % 10;
        if(temp == 4) cnt2++;
        if(temp == 7) cnt3++;
        x/=10;
    }
    if(cnt2 ==0 || cnt3 == 0) return 0;
    else
    {
        if(cnt1 == (cnt2+cnt3))  return 1;
        else            return 0;
    }
}

int main()
{
    IOS

    cin>>n;
    bool luck = calc(n);
    if(luck == 1)   cout<<"YES"<<endl;
    else            cout<<"NO"<<endl;
    return (0);
}