Revert "Revert "Update checkpoints.cpp""

This reverts commit 3693fff36beffa5a87759ac9a21f022ac24de64b.
Revert "Revert "Update main.cpp""

This reverts commit 37d4319dca0ad4992bfc0e666147d231ca87884e.
Revert "Revert "Update main.cpp""

This reverts commit f08b1517f6ed50c6837c5b1c04b7aa6712726799.