#include <fstream>
int zero(int n){
  int nr=0;
  while(n>=5){
    nr+=n/5;
    n/=5;
  }
  return nr;
}
int main()
{FILE *fin, *fout;
 fin=fopen("fact.in", "r");
 fout=fopen("fact.out", "w");
 long long i=0, pas, p;
 fscanf(fin, "%lld", &p);
 pas=1<<30;
 while(pas!=0){
   if(zero(i+pas)<=p-1)
    i+=pas;
   pas/=2;
 }
 if(zero(i+pas)==p)
   fprintf(fout, "%lld", i+1);
 else
   fprintf(fout, "-1");
    return 0;
}