#include <cstdio>

int zero(int n)

{

int p=5,nr=0;

while(n/p>0){nr+=n/p; p*=5;}

return nr;

}

int cbin(int p)

{

int l=1,r=(1<<31)-1,m;

while(l<r)

{

m=((long long)l+r)/2;

if(zero(m)>=p)r=m; else l=m+1;

}

if(zero(r)==p)return r;

return -1;

}

int main()

{

int p;

freopen("fact.in","r",stdin);

freopen("fact.out","w",stdout);

scanf("%d",&p);

printf("%d\n",cbin(p));

return 0;
 

}