#include <cstdio>
#define infile "fact.in"
#define outfile "fact.out"

long long P,N,nr5,nr2;

long long minim(long long x,long long y)
{
      if(x<y)
            return x;
      return y;
}

void solve()
{
      long long i,min=0,aux;

      for(i=1;min<P;i++)
      {
            aux=i;
            while(aux%2==0)
            {
                  nr2++;
                  aux/=2;
            }

            while(aux%5==0)
            {
                  nr5++;
                  aux/=5;
            }

            min=minim(nr2,nr5);
      }

      if(min==P)
            N=i-1;
      else
            N=-1;
}

int main()
{
      freopen(infile,"r",stdin);
      freopen(outfile,"w",stdout);

      scanf("%lld",&P);
      solve();
      printf("%lld\n",N);

      fclose(stdin);
      fclose(stdout);
      return 0;
}