#include<iostream.h>
#include<stdio.h>
#include<string.h>
FILE *f,*g;
int main ()
{
long p,n=0,x=1,x1,nr=0,t=1,n1; int n2;
f=fopen("fact.in","r");       n2=-1;
g=fopen("fact.out","w");
fscanf(f,"%ld",&p);
while(nr<p)
{
n+=1;
x*=n;
x1=x;
nr=0;
while (x1)
{  x1=x1/10;
nr+=1;
}
if(nr==p) { fprintf(g,"%ld",n); fclose(g);}
}
g=fopen("fact.out","r");
fscanf(g,"%ld",&n1);
fclose (g);
if (n1==0) {g=fopen("fact.out","w"); fprintf(g,"%d",n2);   }
fclose(f);
fclose(g);
return 0;
}