View Compilation Error

0_0_17537450_29770.cpp:9:5: error: stray '\' in program
     printf(%lu\n\n",a%2==2?a/2*(a+1):(1+a)/2*a)
     ^
0_0_17537450_29770.cpp:9:5: error: stray '\' in program
0_0_17537450_29770.cpp:9:5: error: missing terminating " character
0_0_17537450_29770.cpp:5:3: error: expected initializer before 'int'
   int a
   ^