Main.cc: In function ‘int main()’: Main.cc:48:9: error: ‘cn’ was not declared in this scope cn+=n; ^~ Main.cc:48:9: note: suggested alternative: ‘c’ cn+=n; ^~ c Main.cc:52:13: warning: unused variable ‘lim’ [-Wunused-variable] int lim=min(n,3ll); ^~~