#include<stdio.h>
int zero(int n)
{
    int nr=0;
    while(n>=5)
    {
        nr=nr+n/5;
        n=n/5;
    }
    return nr;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int p,i=0,pas=1<<16;
    scanf("%d",&p);
    while(pas!=0)
    {
        if(zero(i+pas)<p)
            i=i+pas;
        pas=pas/2;
    }
    printf("%d",i+1);
    return 0;
}