A dangerous spot calculation program causes a computer to extract from risk value information a time to closest point of approach included in a predetermined duration of time. The risk value information stores a closest point of approach and a time to closest point of approach of a first ship and a second ship, in association with a risk value which indicates the probability of collision between the first ship and the second ship at the closest point of approach and the time to closest point of approach. Further, the dangerous spot calculation program causes the computer to acquire, from the risk value information, a closest point of approach and a risk value corresponding to the extracted time to closest point of approach, and to determine to which sea area the acquired closest point of approach belongs. Furthermore, the dangerous spot calculation program causes the computer to sum, with respect to each sea area to which a closest point of approach has been determined to belong, risk values corresponding to the closest point of approach.
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