Solve 743
Add problem 710
Fix problem 50
problem 54
Problem 51
Solve problems 72 and 73
Solve problem 243
Add missing 0
Solve problem 357
Solve problem 99
Solve problem 81
Fix problem 31
Problem 76
Problem 71
Don't lie about times
Add problem 719
Problem 751
Problem 700
Problem 686
Add missing problem20 file