#include<stdio.h>
using namespace std;

long long p,n;

int nr_0(long long a)
{
long long fm=0,factor=5;
while(factor<=a)
    {
    fm+=a/factor;
    factor*=5;
    }
return fm;
}

/*void caut(long long a,long long b)
{
if(nr_0(n)==p)printf("%lld",n);
    else
    {
    n=(a+b)/2;
    if( nr_0(n) < p ) caut(n,b);
    else caut(a,n);
    }
}*/

int main()
{
int gasit=1,nr;
n=1;
freopen("factorial.in","r",stdin);
freopen("factorial.out","w",stdout);
scanf("%lld",&p);
while(gasit)
    {
    nr=nr_0(n);
    if(nr>p){gasit=2;break;}
    else if(nr==p){printf("%lld",n);gasit=0;}
    n++;
    }
if(gasit==2)printf("-1");
//caut(0,900000000);
//printf("%lld",nr_0(p));
return 0;
}