#include<iostream>
#include<fstream>
#include<limits>
#include<cmath>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int x,i,n,j,ok,s;
int main(){
    fin>>n;
    i=1;
    ok=0;
    while(ok==0){
        s=0;
        j=5;
        while(j<=i){
            s+=i/j;
            j*=5;
        }
        if(s==n){
            fout<<i;
            return 0;
        }
        i++;
    }
    return 0;
}