The French rating system considers the overall difficulty of the climb, taking into account the difficulty of the moves and the length of climb. This differs from most grading systems where one rates a climbing route according to the most difficult section (or single move). Grades are numerical, starting at an easy 1, with the system being open-ended. Each numerical grade can be subdivided by adding a letter (a, b or c). Examples: 2, 4, 4b, 6a, 7c. An optional + (but not –) may be used to further differentiate difficulty. Many countries in Europe use a system with similar grades but not necessarily matching difficulties. Sport climbing in Britain and Ireland uses the French grading system, often prefixed with the letter "F".