View Compilation Error

0_0_24589137_29173.cpp: In function 'int dfs(int, int, int, int)':
0_0_24589137_29173.cpp:43:14: error: expected primary-expression before '=' token
     if (a1 < =a2) {
              ^
0_0_24589137_29173.cpp:46:14: error: expected primary-expression before '=' token
     if (b1 < =b2) {
              ^