// Problema factorial

#include <stdio.h>
#define MAX       500000000

long nrz( long c )
{
     long p = 0;
     while( c )
     {
            p += c/5;
            c /= 5;
     }
     return p;
}

int main()
{
    long p;
    freopen( "fact.in", "rt", stdin );
             scanf( "%ld", &p );
    fclose( stdin );
    
    long st = 1;
    long dr = MAX;
    long n = 1;
    long numarz = 0;
    long c = 0;
    while( n )
    {
           if( numarz < p ) st = c+1; else dr = c-1;
           c = ( st+ dr ) /2;
           numarz = nrz( c );
           if( (numarz == p ) && ( st==dr) )
               {
                       n = st;
                       break;                      
               }
           if( dr <= st ) 
               { 
                 n =-1; 
                 break; 
               }
    }
    
           if( (numarz == p ) && ( st==dr) )
               {
                       n = st;
               }
           if( dr <= st ) 
               { 
                 n =-1; 
               }
    
    
    freopen( "fact.out", "wt", stdout );
             printf( "%ld\n", n );
    fclose( stdout );
    return 0;
}