// Problema factorial

#include <stdio.h>

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 n = 0;
    long numarz = 0;
    while( numarz < p )
    {
           n += 5;
           numarz = nrz( n );                      
    }
    if( numarz != p ) n = -1;
    
    freopen( "fact.out", "wt", stdout );
             printf( "%ld\n", n );
    fclose( stdout );
    return 0;
}