#include<bits/stdc++.h>
using namespace std;ifstream f("fact.in");ofstream g("fact.out");long long P,dr,step,i;long long zero(long long n){int sum=0;for(int put=5;put<=n;put*=5)sum+=n/put;return sum;}int main(){f>>P;dr=5*P;for(step=1;step<dr;step<<=1);for(i=1;step;step>>=1){if(i+step<=dr&&zero(i+step)<=P){i+=step;}}while(zero(i)==P&&i>=1)i--;i++;if(zero(i)==P)g<<i<<"\n";else g<<"-1\n";return 0;}