#include <stdio.h>

int zero(int n)
{
    int nr = 0;
    while(n >= 5)
    {
        nr += n / 5;
        n /= 5;
    }
    return nr;
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int p,i = 1,g = 1,z;
    scanf("%d",&p);
    while(g)
    {
        z = zero(i);
        if(z == p){
            printf("%d\n",i);
            g = 0;
        }
        else
            if(z > p){
                printf("-1\n");
            g = 0;
            }
        ++i;
    }
    return 0;
}