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https://d3c33hcgiwev3.cloudfront.net/_d544576262dde3240e03488364d81cae_CourseraProgWeek1Instruction.pdf?Expires=1469404800&Signature=JWxv5nPHi~lodrpxLZMioqJpvsxbIy8Zwcp42n97mrZzyNA2GHuPqFr95ujq19cTiLYM9gtUDZFBryk26bPJgpkRejrwnqahkBHiLSLxD4m9GzfOVo21fhHlF9ZBnoGdhM5KRTwzX4J7GqKiikJMMqNxhDZZ7TNxvG33T7cgju0_&Key-Pair-Id=APKAJLTNE6QMUY6HBC5A