#include <cstdio>
#define infile "fact.in"
#define outfile "fact.out"
#define Max 500024

long long P,N,nr5,nr2;
long long x[Max];

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

void solve()
{
      long long i,aux,nr;

      for(i=1;nr5<P;i++)
      {
            aux=i; nr=0;

            while(aux%5==0)
            {
                  if(x[aux])
                  {
                        nr+=x[aux];
                        aux=1;
                  }
                  else
                  {
                        nr++;
                        aux/=5;
                  }
            }

            x[i]=nr;
            nr5+=nr;

      }

      if(nr5==P)
            N=i-1;
      else
            N=-1;
      if(P==0)
            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;
}