#include <iostream>
#include<fstream>


using namespace std;

int p;

int f(int n)
{int k=0,j=5;
while(j<=n)
{k=k+n/j;
 j=j*5;
}
return k;
}


int cb(int st, int dr)
{int m=(st+dr)/2;
int a;
if(f(m)<p)
   return cb(m+1,dr);
else 
    if(f(m)>p)
     return cb(st,m-1);
    else
    {while(m%5!=0)
        m--;
    if(m==0)
        return -1;
    return m;
    }
    
}


int main()
{int a;
int n=1,x;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
if(p==0)
    g<<"1";
else
   g<<cb(1,2000000000);
g<<endl;



    return 0;
}