View Compilation Error

0_0_29946451_2843.cpp: In function 'void init()':
0_0_29946451_2843.cpp:15:13: error: 'i' was not declared in this scope
         sum[i] = sum[i-1] + i;
             ^
0_0_29946451_2843.cpp: At global scope:
0_0_29946451_2843.cpp:21:5: error: expected initializer before 'll'
     ll ans = 1;
     ^
0_0_29946451_2843.cpp:22:5: error: expected unqualified-id before 'while'
     while(b)
     ^
0_0_29946451_2843.cpp:28:5: error: expected unqualified-id before 'return'
     return ans;
     ^
0_0_29946451_2843.cpp:29:1: error: expected declaration before '}' token
 }
 ^