foo.cc: In function 'int main()':
foo.cc:16:21: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   f[i & 1][0] = f[i - 1 & 1][1];
                   ~~^~~
foo.cc:17:22: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   f[i & 1][1] = (f[i - 1 & 1][0] + f[i - 1 & 1][2]) % mod;
                    ~~^~~
foo.cc:17:40: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   f[i & 1][1] = (f[i - 1 & 1][0] + f[i - 1 & 1][2]) % mod;
                                      ~~^~~
foo.cc:18:22: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   f[i & 1][2] = (f[i - 1 & 1][1] + f[i - 1 & 1][3]) % mod;
                    ~~^~~
foo.cc:18:40: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   f[i & 1][2] = (f[i - 1 & 1][1] + f[i - 1 & 1][3]) % mod;
                                      ~~^~~
foo.cc:19:21: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
   f[i & 1][3] = f[i - 1 & 1][2];
                   ~~^~~
foo.cc:22:15: warning: suggest parentheses around '+' in operand of '&' [-Wparentheses]
  cout << (f[n + 1 & 1][1] + f[n + 1 & 1][2]) % mod;
             ~~^~~
foo.cc:22:33: warning: suggest parentheses around '+' in operand of '&' [-Wparentheses]
  cout << (f[n + 1 & 1][1] + f[n + 1 & 1][2]) % mod;
                               ~~^~~

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