def findLongestRun(runLogs):
    max_len = 0
    max_proc = 0
 
    prev_end = 0  # first process starts at time 0
 
    for proc, end_time in runLogs:
        run_length = end_time - prev_end
        if run_length > max_len:
            max_len = run_length
            max_proc = proc
        prev_end = end_time
 
    return chr(max_proc + ord('a'))
 
 
# Example test
# runLogs = [(0, 3), (2, 5), (0, 9), (1, 15)]
# runLogs = [(0,2), (1,3), (0,7)]
runLogs = [(0,1), (0,3), (4,5), (5,6), (4,10)]
print(findLongestRun(runLogs))  # Output: 'b'
 

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