110A *800

110А
    long int n, k = 0, f = 1;
    cin >> n;
    while(n!=0){
        if(n%10==7 || n%10==4){k++;}
        n /= 10;
    }
    while(k!=0){
        if(k%10 != 4 && k%10 != 7){f = 0;}
        k /= 10;
    }
    if(f==1){cout << "YES";}
    else{cout << "NO";}