#include <fstream>
using namespace std;
 
ifstream fin ("fact.in");
ofstream fout ("fact.out");
 int m,N=1000000000;
int numarZero(int n){
    int s=0;
    if(n==0) return 1;
 for(long long i=5;n/i>=1;i*=5)
        s+=n/i;
    return s;
}
int cautBinara(int p){
    int s=0,d=N,z;
    while(s<=d){
        m=( s + d ) / 2;
        z = numarZero(m);
        if(p == z) {
            int x=m;
            
            while(numarZero(x) == z)
            x--;
            
            return x+1;}
        if(p > z)
        {
            s = m + 1;
        }
        if(p < z)
        {
            d = m - 1;
        }
        
    }
}
int main ()
{
    long long P,auxP=0,i=1,N;
    fin >> P;
    fout<<cautBinara(P);
    
}