Quarterly report pursuant to Section 13 or 15(d)

Stock Options and Warrants (Detail)

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Stock Options and Warrants (Detail) - USD ($)
 6 Months Ended 12 Months Ended
Nov. 30, 2019
May 31, 2019
Stock option and warrant activity    
Options and warrants outstanding, Number of Shares 178,591,849  
Granted, Number of Shares 30,756,055  
Exercised, Number of Shares (30,250,649)  
Forfeited/expired/cancelled, Number of Shares (1,640,000)  
Options and warrants outstanding, Number of Shares 177,457,255 178,591,849
Outstanding exercisable, Number of Shares 173,178,551  
Options and warrants outstanding, Weighted Average Exercise Price $ 0.71  
Granted, Weighted Average Exercise Price 0.36  
Exercised, Weighted Average Exercise Price 0.39  
Forfeited/expired/cancelled, Weighted Average Exercise Price 0.74  
Options and warrants outstanding, Weighted Average Exercise Price 0.65 $ 0.71
Outstanding exercisable, Weighted Average Exercise Price $ 0.66  
Options and warrants outstanding, Weighted Average Remaining Contractual Life in Years 3 years 8 months 1 day 3 years 9 months
Outstanding exercisable, Weighted Average Remaining Contractual Life in Years 3 years 6 months 21 days  
Options and warrants outstanding, Aggregate Intrinsic Value $ 0 $ 896,400
Outstanding exercisable, Aggregate Intrinsic Value $ 0