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#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n,p,i;
int fo(int n)
{ int r=0,p5=5;
while(n>=p5)
{ r=r+n/p5;
p5=p5*5;
}
return r;
}
int main()
{ f>>p;
int st=1,dr=500000000;
while(st<=dr)
{ int mij=(st+dr)/2;
if(fo(mij)<p) st=mij+1;
else dr=mij-1;
}
if(fo(st)==p) g<<st;
else g<<"-1";
g.close(); return 0;
}