#include <stdio.h>
#include <vector>
#define infile "fact.in"
#define outfile "fact.out"
#define nmax 100

using namespace std;

long p, i, j, nr;
vector <int> c;

void readdata();
void writedata();
void solve();

int main()
{
 readdata();
 if (!p) { freopen(outfile, "w", stdout); printf("1\n"); fclose(stdout); }
 else
     {
      solve();
      writedata();
     }
 return 0;
}

void readdata()
{
 freopen(infile, "r", stdin);
 scanf("%ld", &p);
 fclose(stdin);
}

void solve()
{
 long temp;
 c.push_back(0);
 for (i=5; nr<p; i+=5)
     {
      for (j=1; j<=4; j++) c.push_back(0);
      c.push_back(1+c[i/5]);
      nr+=c[i];
     }
}

void writedata()
{
 freopen(outfile, "w", stdout);
 if (nr==p) printf("%d\n", i-5);
 else printf("-1\n");
 fclose(stdout);
}