View Compilation Error

0_0_28834129_29382.cpp: In function 'void Solve()':
0_0_28834129_29382.cpp:41:12: error: 'fx' was not declared in this scope
    if(mark[fx])mark[a]=1;
            ^
0_0_28834129_29382.cpp:42:12: error: 'fy' was not declared in this scope
    if(mark[fy])mark[b]=1;
            ^
0_0_28834129_29382.cpp:43:7: error: 'fx' was not declared in this scope
    if(fx==fy||mark[a]&&mark[b]) {
       ^
0_0_28834129_29382.cpp:43:11: error: 'fy' was not declared in this scope
    if(fx==fy||mark[a]&&mark[b]) {
           ^