foo.c: In function 'main':
foo.c:6:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    6 |  scanf("%d",&j);
      |  ^~~~~
foo.c:6:2: warning: incompatible implicit declaration of built-in function 'scanf'
foo.c:2:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
    1 | #include<math.h>
  +++ |+#include <stdio.h>
    2 | int main()
foo.c:20:12: error: 'l' undeclared (first use in this function)
   20 |  for(y=2;y<l;y++)
      |            ^
foo.c:20:12: note: each undeclared identifier is reported only once for each function it appears in
foo.c:24:4: error: 'O' undeclared (first use in this function)
   24 |  k=O;
      |    ^
foo.c:30:3: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   30 |   printf("%d+%d=%d\n",n,k,j);
      |   ^~~~~~
foo.c:30:3: warning: incompatible implicit declaration of built-in function 'printf'
foo.c:30:3: note: include '<stdio.h>' or provide a declaration of 'printf'

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