#include<iostream.h>
#include<stdio.h>

  long numarzerouri( long c )
{
     long p = 0;
     while( c )
     {
            p += c/5;
            c /= 5;
     }
     return p;
}
      

int main()
{
long int st, dr, n, p, c, nrz;

freopen("fact.in", "r", stdin);
freopen("fact.out", "w", stdout);

cin>>p;

st=0;
dr=1000000000;
n=1;
if(p>0)
{
while(n)
      {  c=(st+dr)/2;
              nrz=numarzerouri(c);
	      if(nrz==p && st==dr)
	      { n=st; break;} 
	      if(dr<st)
	       { n=-1; break;} 
	      if(p>nrz)
	        st=c+1;
	      else
	        dr=c-1;                            
      }
}

cout<<dr; 

return 0;
}