If length of string is single digit then it 's not divisible by 25
n = str . length ; if ( n == 1 ) return false ; return ( ( str [ n - 1 ] - ' ' == 0 && str [ n - 2 ] - ' ' == 0 ) || ( ( str [ n - 2 ] - ' ' ) * 10 + ( str [ n - 1 ] - ' ' ) ) % 25 == 0 ) ; }