foo.cc: In function 'int dfs(int, int)':
foo.cc:46:19: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
             if (f = dfs(TO[i], min(a, V[i]))) {
                 ~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:70:25: warning: unused variable 'x' [-Wunused-variable]
         for (int j = 0, x; j < n; ++j) {
                         ^
foo.cc:76:25: warning: unused variable 'x' [-Wunused-variable]
         for (int j = 0, x; j < n; ++j) {
                         ^
foo.cc:68:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &m, &n);
     ~~~~~^~~~~~~~~~~~~~~~
foo.cc:71:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d", &A[i][j]);
             ~~~~~^~~~~~~~~~~~~~~~

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