foo.c: In function ‘main’:
foo.c:4:2: error: ‘a’ undeclared (first use in this function)
    4 | {a=int(input())
      |  ^
foo.c:4:2: note: each undeclared identifier is reported only once for each function it appears in
foo.c:4:4: error: expected expression before ‘int’
    4 | {a=int(input())
      |    ^~~