AMO · 2027 · Grades 6-7 · Self-study SET 30 Question 11

Four sisters paint at the same constant rate and take turns, with no overlap or gaps. Alice finishes $1/4$ of the job; then Beth finishes $2/3$ of what is left; then Cathy finishes $3/4$ of the new remainder. Dee completes the last part in 20 minutes. How many minutes does the entire job take?

**Input:** Enter the integer only, without units.