the past. Some countries apply the principle of reciprocity in their visa policy. A country's visa policy is called 'reciprocal' if it imposes visa requirement against citizens of all the countries that impose visa requirements against its own citizens. The opposite is rarely true: a country rarely lifts visa requirements against citizens of all the countries that also lift visa requirements against its own citizens, unless a prior bilateral agreement has been made. A fee may be charged for issuing a visa; these are often also reciprocal—hence, if country A charges country B's citizens US$50 for a visa, country B will often also charge the same amount for country A's visitors. The fee charged may also be at the discretion of each embassy. A similar reciprocity often applies to the duration of the visa (the period in which one is permitted to request entry of the country) and the number of entries one can attempt with the visa. Other restrictions, such as requiring fingerprints and photographs, may also be reciprocated. Expedited processing of the visa application for some countries will generally incur additional charges. Government authorities usually impose administrative entry restrictions on foreign citizens in three ways - countries whose nationals may enter without a visa, countries whose nationals may obtain a visa on arrival, and countries whose nationals require a visa in advance. Nationals who require a visa in advance are usually advised to obtain them at a diplomatic mission of their destination country. Several countries allow nationals of countries that require a visa to obtain them online. The following table lists visa policies of all countries by the number of foreign nationalities that may enter that country for tourism without a visa or by obtaining a visa on arrival with normal passport. It also notes countries that issue electronic visas to certain nationalities. Symbol "+" indicates a country that limits the visa-free regime negatively by only listing nationals who require a visa, thus the number represents the number of UN member states reduced by the number of nationals who require a visa and "+" stands for all possible non-UN member state nationals that might also not require a visa. "N/A" indicates countries that have contradictory information on its official websites or information supplied by the Government to IATA. Some countries that allow visa on arrival do so only at a limited number of entry points. Some countries such