#include<fstream>
using namespace std;

ifstream cin("fact.in");
ofstream cout("fact.out");
/*
int sumcif(int n){
   int sum = 0;
   while(n){
      sum += n % 10;
      n /= 10;
   }
   return sum;
}
*/
int zero(int n){

    int p = 5, s = 0;
    while(p <= n)
        s += n / p, p *= 5;

    return s;
}

int CautBin(int p){
   if(p == 0)
      return 1;
   long long st = 5, dr = 10000000;
   while(st <= dr){
      long long mij = (st + dr) / 2;
      if(zero(mij) == p)
         return mij;
      else if(zero(mij) < p)
          st = mij + 1;
      else
          dr = mij - 1;
   }
   return -1;
}

int main(){

   int p;
   cin >> p;
   cout << CautBin(p);

   return 0;
}