#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    long p,s;    
    int y,nr,n;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    s=1;
    nr=0; n=1;
    while(nr<=p)
    {
        y=n;
        s=s*n;        
         n++;
        while(y%5==0 && nr<=p) 
        {
                   if(y%5==0)
                   nr++;
                   y/5;
                   }        
}
g<<n-1;
return 0;
}