#include <cstdio>

using namespace std;

FILE * fin=fopen("fact.in","r");
FILE * fout=fopen("fact.out","w");
int getAparitii(int n)
{
    int ct=0;
    while (n%5==0){
        ct++;
        n/=5;
    }
    return ct;
}
int f(long long int n)
{
    if (n/5==0)
        return 0;
    else return n/5+f(n/5);
}
int main()
{
    int p;
    long long int n;
    fscanf(fin,"%d",&p);
    long long int a,b,c,x;
    a=1;
    b=100000000;
    c=(a+b)/2;
    x=f(c);
    while (x!=p){
        if (x>p)
            b=c-1;
        else
            a=c+1;
        c=(a+b)/2;
        x=f(c);
    }
   /* while (f(c-1)==p)
        c--;*/
    fprintf(fout,"%d",c-c%5);
}