function zeros(expression) {
  let arr = expression.split('*');
  let counter = 0;
  let count = 0;

  let factorial = arr.filter(item => item.includes("!!") == false);
  let fact = factorial.map(function(item) {
    let value1 = +item.slice(0, -1);
    return value1;
  });
  let doubleFactorial = arr.filter(item => item.includes("!!") == true);
  let doubleFact = doubleFactorial.map(function(item) {
    let value1 = +item.slice(0, -2);
    return value1;
  });

  let zeroFactorial = fact.map(function(n) {
    if ( n % 2 == 0  && n < 5) {
    	return 2;
    } else if ( n == 1) {
        return 1;
    } else {
    	let counter1 = 0;
	    for (let i = 5; n/i >= 1; i *= 5)
	    counter1 *= Math.pow(10,Math.floor(n/i));
		return counter1*2;
    };
  });

  let zeroDoubleFactorial = doubleFact.map(function(n) {
    if ( n % 2 == 0  && n < 10) {
    	return 2;
    } else if ( n % 2 != 0 && n > 3) {
        return 5;
    } else if ( n <= 3) {
        return 1;
    } else {
    	let counter2 = 0;
	    for (let i = 10; n/i >= 1; i *= 5)
	    counter2 *= Math.pow(10,Math.floor(n/i));
	    return counter2*2;
    };
  });


  
  counter = arrayfunc(zeroFactorial) * arrayfunc(zeroDoubleFactorial);

  howMuch(counter);
  alert (count);


function arrayfunc(array){
  let pr = 1;
  for(let j = 0; j < array.length; j++){
      pr *= array[j];
  };
  return pr;
};

function howMuch(num){
  for(let x = 10; num % x == 0; x = x*10){
      count ++;
  };
};
};
zeros('100!!');