View Compilation Error

0_0_13796291_13036.cpp:52:9: error: stray '\' in program
         LL sum = num * PreSum(x\num);
         ^
0_0_13796291_13036.cpp: In function 'void dfs(int, int, int, int, int, int)':
0_0_13796291_13036.cpp:52:33: error: expected ')' before 'num'
         LL sum = num * PreSum(x\num);
                                 ^