Main.c: In function ‘main’:
Main.c:5:11: warning: self-comparison always evaluates to true [-Wtautological-compare]
    5 |  for(n=1;n<=n;n++)
      |           ^~
Main.c:6:9: error: ‘s’ undeclared (first use in this function)
    6 |         s=s+n;
      |         ^
Main.c:6:9: note: each undeclared identifier is reported only once for each function it appears in