#include<cstdio>
const int N=1<<9;
int p;
int zero (int n)
{ 
int s=0;
while (n);
{
	s+=n/5;
	n/=5;
}
return s;
}

int fact(int p)
{
	int i,pas=N;
	for ( i=0; pas;pas>>1)
    if (zero(i+pas)<p)
		i+=pas;
	return (i+1);
}
int main()
{
freopen("uscat.in","r",stdin);
freopen("uscat.out","w",stdout);
scanf("%d",&p);
int k=fact(p);
printf("%d",k);
return(0);
}