islands.adb:19:20: medium: precondition might fail, cannot prove i in N_Range (e.g. when i = 4)[#0]
islands.adb:20:20: medium: precondition might fail, cannot prove i in N_Range (e.g. when i = 1)[#1]
islands.adb:21:20: medium: precondition might fail, cannot prove j in M_Range (e.g. when j = 5)[#2]
islands.adb:22:20: medium: precondition might fail, cannot prove j in M_Range (e.g. when j = 1)[#3]
islands.adb:40:31: medium: overflow check might fail[#4]
islands.ads:35:14: medium: postcondition might fail, cannot prove Count_Islands'Result < (N * M)[#5]
