#include<cstdio>
#include<climits>

int nr0f(int n)
{
    int no=0,put=5;
    for(put=5; put<=n; put*=5)
        no+=n/put;
    return no;
}

int main()
{
    int p,m,li=1,lf=INT_MAX-1,no;
    FILE *f=fopen("fact.in","r");
    fscanf(f,"%d", p);
    while(li<=lf)
    {
        m=(li+lf)/2;
        no=nr0f(m);
        if(no<=m)
            lf=m-1;
        else
            li=m+1;
    }
    f=fopen("fact.out","w");
    if(nr0f(li)==p)
        fprintf(f, "%d",li);
    else fprintf(f, "-1");
}