In Codeforces Round #538 (Div. 2), I submitted the solution for problem C and got WA on test case 4 ( solution link ). I checked it offline and it gave correct output for test case 4. I also checked it on online compiler ideone, and it also gave the correct result. I tried submitting in different versions of C++ ( an illogical attempt and so )... failed. Please help me to find the cause of ambiguity ?