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

bool verif(int p, int n) 
{ 
    int copie = p, nr = 0, f = 5; 
    while (f <= copie) 
    { 
        nr += copie/f; 
        f = f*5; 
    } 
    return (nr >= n); 
} 
  

int cautareB(int n) 
{ 
	if (n==0)
		return 1;
     
    if (n==1) 
        return 5; 
  
    
    int li = 0,ls=5*n;// numarul e cuprins intre 0 si 5*n
  
     
    while (li <ls) 
    { 
        int mid = (li + ls)/2; 
   
        if (verif(mid, n)) 
            ls = mid; //stop
        else
            li = mid+1; 
    } 
  
    return li; 
} 
  

int main() 
{ 	
	ifstream f("fact.in");
	ofstream f1("fact.out");
    int n;
    f>>n;
    f1<<cautareB(n); 
    return 0; 
}