foo.cpp:12:5: error: stray '\243' in program
     if (f[l][r]！=-1) return f[l][r];
     ^
foo.cpp:12:5: error: stray '\241' in program
foo.cpp: In function 'int dfs(int, int)':
foo.cpp:12:21: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     if (f[l][r]！=-1) return f[l][r];
                     ^