#include <stdio.h>
int p;
FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");

inline void citire()
{
    fscanf(f,"%d",&p);
}

void afisare(long x)
{
    fprintf(g,"%ld",x);
}

void solve()
{
    long i=0,g=0,aux;
    while (g<p)
    {
        i++;
        aux=i;
        while (aux%5==0) {g++;aux=aux/5;}
    }
    if (g==p) afisare(i);
    else afisare(-1);
}

int main()
{
    citire();
    solve();
    fclose(f);
    fclose(g);
    return 0;
}