#include<fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
long p,i,k,j,q;
int main()
{int gasit=0;
f>>p;
if(p==0)
g<<1;
else
	for(i=5,j=1;i<=10000000000,j<=1973124&&!gasit;i+=5,j++)
		{if(i%390625==0)
			k+=8;
		 else
			 if(i%78125==0)
				 k+=7;
			 else
				 if(i%15625==0)
					 k+=6;
				 else
					 if(i%3125==0)
						 k+=5;
					 else
						 if(i%625==0)
							 k+=4;
						 else
							 if(i%125==0)
								 k+=3;
							 else
								 if(i%25==0)
									 k+=2;
								 else
									 k++;
        if(k==p)
		{gasit=1;g<<i;}
		if(k>p)
		{g<<-1;gasit=1;}
		}
return 0;
}