/in/foo.c: In function 'main':
/in/foo.c:30:23: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    if(k1>=11||k2>=11&&abs(k1-k2)>=2){
                       ^~~
/in/foo.c:30:21: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    if(k1>=11||k2>=11&&abs(k1-k2)>=2){
               ~~~~~~^~~~~~~~~~~~~~~
/in/foo.c:56:21: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    if(k1>=21||k2>=21&&abs(k1-k2)>=2){
               ~~~~~~^~~~~~~~~~~~~~~