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int ffs (x) int x; { int bit, mask; if (x == 0) return 0; for (bit = 1, mask = 1; !(x & mask); bit++, mask <<= 1) ; return bit; } f (x) int x; { int y; y = ffs (x) - 1; if (y < 0) abort (); } main () { f (1); exit (0); }