View Compilation Error

0_0_24413953_20642.cpp: In function 'void Union(int, int)':
0_0_24413953_20642.cpp:48:9: error: 'flag' was not declared in this scope
         flag = 1;
         ^
0_0_24413953_20642.cpp: In function 'int main()':
0_0_24413953_20642.cpp:54:12: error: 'a' was not declared in this scope
         if(a == -1 && b == -1)
            ^
0_0_24413953_20642.cpp:54:23: error: 'b' was not declared in this scope
         if(a == -1 && b == -1)
                       ^
0_0_24413953_20642.cpp:57:12: error: 'a' was not declared in this scope
         if(a == 0 && b == 0) {
            ^
0_0_24413953_20642.cpp:57:22: error: 'b' was not declared in this scope
         if(a == 0 && b == 0) {
                      ^
0_0_24413953_20642.cpp:67:13: error: 'maxn' was not declared in this scope
             maxn = -1;
             ^