#include <fstream.h>
#define max 100000;
ifstream g("fact.txt");
ofstream h("fact.out");
long b=max;
long p;

long f(long x){
    long nr,c;
    nr=0;
    while(x>0){
              c=x;
                if (c % 5 == 0)
                while (c % 5 == 0)
                    {nr++;
                    c/=5;}
                    else c--;
                        x--;}
                                  return nr;
                                  }
long caut(long a, long b)
{ long m;

    while (a <= b) {
        m = (a + b) / 2;
        if (f(m) <= p)
            a = m + 1;
        else
            b = m - 1;
    }
    m = (a + b) / 2;

    while(f(m) == p) m --;
            h<<++m;
   }
int main(){
    g>>p;
    caut(0,b);
    return 0;
}