/in/foo.c: In function 'prime':
/in/foo.c:9:9: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(i>=n&&n!=1||n==2)
     ~~~~^~~~~~
/in/foo.c: In function 'cprime':
/in/foo.c:19:4: error: 'i' undeclared (first use in this function)
    i++;
    ^
/in/foo.c:19:4: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:20:3: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
   else
   ^~~~
/in/foo.c:22:4: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'else'
    n=n/10;
    ^