foo.c: In function 'main':
foo.c:12:8: warning: implicit declaration of function 'solve' [-Wimplicit-function-declaration]
    if (solve(a, i, j, m, n) == 1)
        ^~~~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &m, &n);
  ^~~~~~~~~~~~~~~~~~~~~
foo.c:9:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d", &a[i][j]);
    ^~~~~~~~~~~~~~~~~~~~~

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