foo.cpp: In function 'int main()':
foo.cpp:66:30: error: redeclaration of 'int i600'
   for(int j=i*300,i600=i*600,i600=i600; j<=i600; j++) {
                              ^
foo.cpp:66:19: error: 'int i600' previously declared here
   for(int j=i*300,i600=i*600,i600=i600; j<=i600; j++) {
                   ^