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

long f( long c )
{
     long p = 0;
     while( c )
     {
            p += c/5;
            c /= 5;
     }
     return p;
}
void 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;
}