#include <iostream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int nz(int x)
{
    int ans = 0, p5=5;
    while(x>=p5)
    {
        ans=ans+(x/p5);
        p5*=5;
    }
    return ans;
}

int main() {
    int p;
    in>>p;
    int st = 1, dr = 5*p;
    while(st<=dr)
    {
        int mijl = (st+dr)/2;
        if(nz(mijl)<p) st = mijl+1;
        else dr = mijl-1;
    }
    if(nz(st) == p) out<<st;
    else out<<"-1";
    return 0;
}