#include<stdio.h>
int main()
{long i,r,kmax,p,nrsol=0,ok=1,n;
FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");
i=5;
kmax=25;
r=1;
fscanf(f,"%ld",&p);
if (p==0) fprintf(g,"1");
else
{while (nrsol<=p&&ok==1)
	{if (i%kmax==0) {r++; nrsol+=r; if (nrsol==p){ok=0; n=i; }
												else if (nrsol>p) {ok=0; n=-1;}
							kmax=kmax*5;}
	 else {nrsol++;if (nrsol==p) {ok=0; n=i;}}
	 i+=5;}
fprintf(g,"%ld",n);   }
fclose(f);
fclose(g);
return 0;
}