#include<iostream.h>
#include<math.h>
#include<fstream.h>

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

int x,exmax,i,t,y;


int putere(int x)
{int a=5; int i=0;

while(a<=x)
{
a*=5;
i++;
}
return i;
}

int suma(int a, int b)
{int s=0;
 for(i=b;i>=1; i--)s+=(a/(pow(5,i)));

return s;
}



int main()
{

f>>x;y=5*x;t=0;
while(t!=x)
{exmax=putere(y);

t=suma(y,exmax);
y-=5;
}
if(x==0)g<<1; else
g<<y+5;
}