prog.cpp: In function ‘int main()’:
prog.cpp:13:12: error: ‘a1’ was not declared in this scope
if(b==a*2&&a1+a2==a*3&&b+a2+a3==a*5){
^~
prog.cpp:13:15: error: ‘a2’ was not declared in this scope
if(b==a*2&&a1+a2==a*3&&b+a2+a3==a*5){
^~
prog.cpp:13:29: error: ‘a3’ was not declared in this scope
if(b==a*2&&a1+a2==a*3&&b+a2+a3==a*5){
^~
prog.cpp:14:24: error: ‘end1’ was not declared in this scope
cout<<b<<""<<c<<""<<d<<end1}
^~~~