#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int p;
int putere(int n){
    int r=0;
    while(n>=1){
        r+=n/5;
        n/=5;
    }
    return r;
}
int main(){
    int b,i,pas=(1<<30);
    f>>p;
	for(i=0;pas!=0;pas/=2) if(putere(i+pas)<p)i+=pas;
    b=i+1;
    if(putere(b) == p) g<<b;
    else g<<-1;
    return 0;
}