#include <iostream>

using namespace std;

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


int main()
{
 ifstream cin("fact.in");
 ofstream cout("fact.out");
 int P, rez=0;
 cin>>P;
 if(P==0){
     cout<<1;
 }
 else{
 for(int i=0; i<P*5+25; i++){
     if(nrZero(i)==P){
         rez=i;
         break;
     }
 }
 cout<<rez;
 }

    return 0;
}