Main.c: In function ‘main’: Main.c:8:23: warning: suggest parentheses around comparison in operand of ‘&’ [-Wparentheses] if(n%4==0&&n%100!=0||n&400==0) cout<<"Yes"; ^ Main.c:8:10: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(n%4==0&&n%100!=0||n&400==0) cout<<"Yes"; ~~~~~~^~~~~~~~~~ Main.c:8:32: error: ‘cout’ undeclared (first use in this function) if(n%4==0&&n%100!=0||n&400==0) cout<<"Yes"; ^~~~ Main.c:8:32: note: each undeclared identifier is reported only once for each function it appears in Main.c:5:1: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &t); ^~~~~~~~~~~~~~~ Main.c:7:1: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^~~~~~~~~~~~~~~