Pilgrims in Ujjain were asked which of two temples they visited that morning; the number outside the circles visited neither. How many pilgrims visited the Harsiddhi temple?

The Harsiddhi circle holds the Harsiddhi-only part and the shared part: $22+15=37$. 22 counts only those who visited Harsiddhi alone, 42 is the Mahakal circle $27+15$, and 64 is everyone who visited at least one temple.