Operation Instructions：
1.The program is used to measure the running time for three functions which calculate X^N.

2.At the beginning of the program, you will see the menu below:

Welcome to Use The Program for Performance Measure
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0.Exit
1.Algorithm 1
2.Algorithm 2(iterative version)
3.Algorithm 2(recursive version)

Notice:If N and K you input is floating point number,
the program will conside it only the integral part!

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Then you could make your choices(0 to 3), and then you can input X, N and the running times K, you will get the result.

3.WARNING:DO NOT INPUT ANY CHARACTER IN THE PROGRAM, IT MAY CAUSE A DEATH CIRCULATION.