PROGRAM FACTORIAL;        {~~~METODA CLASICA~~~}
{------------------------------------------------}
FUNCTION NR_FACT_5(K:LONGINT):BYTE;
{Returneaza numarul factorilor de 5 din descompunerea numarului K.}
VAR NR:BYTE;
BEGIN
NR:=0;
WHILE (K MOD 5 = 0) DO BEGIN
                       NR:=NR+1;
                       K:=K DIV 5;
                       END;
NR_FACT_5:=NR;
END;
{------------------------------------------------}
VAR N,P,NR0:LONGINT;
    F,G:TEXT;
BEGIN
ASSIGN(F,'fact.in'); RESET(F);
ASSIGN(G,'fact.out'); REWRITE(G);
READ(F,P);
IF (P=0) THEN N:=1
         ELSE N:=0;
NR0:=0;   {NR0= nr. cifrelor de zero de la finalul lui N factorial!}
WHILE (NR0<P) DO BEGIN
                 N:=N+5;
                 NR0:=NR0 + NR_FACT_5(N);
                 END;
IF (NR0=P) THEN WRITE(G,N)
           ELSE WRITE(G,-1);
CLOSE(F); CLOSE(G);
END.