/in/foo.c: In function 'main':
/in/foo.c:14:9: warning: statement with no effect [-Wunused-value]
         for (u; u > n - i; u--)
         ^
/in/foo.c:19:9: warning: statement with no effect [-Wunused-value]
         for (d; d < i; d++)
         ^
/in/foo.c:25:5: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long long int' [-Wformat=]
     printf("%d\n", ans);
     ^