#include <fstream>
std::ifstream f;
std::ofstream g;

int n_zero(int n){
    int x=5,p=0;
    while(n/x>0){p+=n/x;x*=5;}
    return p;
}

int cb(int p){
    int n=0,k;
    int st=0,dr=0x17d78410,mid;
    while(st<dr){
        mid=(st+dr)/2;
        k=n_zero(mid);
        if(p>k)st=mid+1;else dr=mid-1; };
    return mid;
}

int main(){
    int p,n;
        f.open("fact.in");
        g.open("fact.out");
        f>>p;
        n=cb(p);
        g<<(n_zero(n)==p?n:-1);
}