Read this article and answer this question Mairesse secured third place in the Grand Prix of Monza in June 1959. Driving a Scuderia Ferrari, he placed behind Alfonso Thiele and Carlo Mario Abate, both also in Ferraris. Mairesse and Mike Parkes of England finished second to Phil Hill and Olivier Gendebien at the 1961 24 Hours of Le Mans. Driving a Scuderia Ferrari, Mairesse and Parkes also eclipsed the previous Le Mans record, covering 2,758.66 miles. In the 1963 12 Hours of Sebring Mairesse and Nino Vacarella placed second after Ludovico Scarfiotti and John Surtees. Both teams drove Ferraris. Surtees and Mairesse won the 1000 km of the Nurburgring driving a Ferrari 250P. Thereafter, Surtees and Mairesse led for the  15 hours of the first 18 hours of the 1963 24 Hours of Le Mans before the car caught fire while Mairesse was driving.  Mairesse escaped injury. Scarfiotti and Lorenzo Bandini won on the French circuit where Christian Heins had a fatal accident. Mairesse and Surtees retired after a motor fire. A young German Red Cross worker was killed in August 1963 when the wheel of a Ferrari driven by Mairesse came off as his car overturned. Guenther Schneider, 19, was hit by a flying wheel during the running of the German Grand Prix at the Nürburgring and died. Mairesse was triumphant in the 1964 Grand Prix of Angola, run at Luanda. His average speed was 80.78 miles per hour. Mairesse piloted a Ferrari 250 LM to first place in the Grand Prix of Spa in May 1965. He completed the race in 2 hours, 29 minutes, and 45.7 seconds. He averaged 126.29 seconds. Mairesse and Jean Beurlys of France finished third at the 1965 24 Hours of Le Mans in a Ferrari 275 GTB winning the GT category in its debut at Le Mans, while Masten Gregory and Jochen Rindt won the race. In April 1966 Surtees and Parkes won the 1,000 kilometer Autodromo Nazionale Monza Auto Race. Mairesse and Herbert Mueller of Switzerland came in third in a Ford sports car, two laps behind. In May Mairesse and Mueller drove to victory in the Targa Florio, driving a Porsche Carrera 6. Rain caused considerable attrition as only thirteen of seventy starters finished the race. Mairesse and Beurlys again drove a Ferrari to third place in the 1967 24 Hours of Le Mans. This event was won by the American team of Dan Gurney and A. J. Foyt.
How many starters finished the race?
13