0_0_39682987_7546.cpp: In function 'int main()': 0_0_39682987_7546.cpp:5:5: error: expected initializer before 'cin' 5 | cin>>a; | ^~~ 0_0_39682987_7546.cpp:7:22: error: 'a' was not declared in this scope 7 | cout <<(int)(a/2*(1+a))<<endl; | ^