Main.cc: In function ‘int main()’: Main.cc:13:2: warning: this ‘for’ clause does not guard... [-Wmisleading-indentation] for (int i =0 ;i <=sqrt(a);i++) ^~~ Main.cc:17:3: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘for’ { sum=sum+i; ^ Main.cc:17:13: error: ‘i’ was not declared in this scope { sum=sum+i; ^ Main.cc:9:6: warning: unused variable ‘b’ [-Wunused-variable] int b ; ^