 Complete the following phrase:  This is a list of host cities of the Olympic Games, both summer and winter, since the modern Olympics began in 1896. Since then, summer and winter games have usually celebrated a four-year period known as an Olympiad; summer and winter games normally held in staggered even years. There have been 28 Summer Olympic Games held in 23 cities, and 23 Winter Olympic Games held in 20 cities. In addition, three summer and two winter editions of the games were scheduled to take place but later cancelled due to war: Berlin summer in 