#include <stdio.h>
using namespace std;

int main(void)
{FILE *fin=fopen("fact.in","r");
 FILE *fout=fopen("fact.out","w");
 long long nr,x,i;
 int p;
 fscanf(fin,"%d",&p); fclose(fin);
 if(p==0){fprintf(fout,"1"); fclose(fout); return 0;	}
 nr=x=i=0;
 while(p>0)
	{i++; p--;
	 if(i%5==0){x=i;while(x%5==0){p--;x/=5;	}	}
	}
 if(p<0)fprintf(fout,"-1");
 else fprintf(fout,"%lld",i*5);
 fclose(fout);
 return 0;
}