#include <fstream>
using namespace std;

ifstream f("factorial.in");
ofstream g("factorial.out");

long long P,x=0,y=0,z,i;

int main()
{f>>P;

while(x<P)
{i=0;
    y=y+5;
z=y;
while(z%5==0)
{z=z/5;
i=i++;}
    x=x+i;
}

if(x>P)
g<<"-1";

else
g<<y;

    return 0;
}