#include <fstream>
using namespace std;ifstream f("fact.in");ofstream g("fact.out");int P,st,dr,mij;int nrz(int x) {int pow=5,rez=0;while(x>=pow)rez+=(x/pow),pow*=5;return rez;}int main(){f>>P;st=1,dr=5*P;while(st<=dr){mij=(st+dr)/2;if(nrz(mij)<P)st=mij+1;else dr = mij-1;}if(nrz(st)==P) g<<st<<"\n";else g<<"-1\n";return 0;}