/in/foo.c:3:1: error: unknown type name 'using'
 using namespace std;
 ^~~~~
/in/foo.c:3:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
 using namespace std;
                 ^~~
/in/foo.c: In function 'readstr':
/in/foo.c:7:9: error: 's' redeclared as different kind of symbol
     int s[100];
         ^
/in/foo.c:5:19: note: previous definition of 's' was here
 int readstr(char* s){
                   ^
/in/foo.c:7:9: warning: variable 's' set but not used [-Wunused-but-set-variable]
     int s[100];
         ^
/in/foo.c: In function 'main':
/in/foo.c:16:11: warning: implicit declaration of function 'min' [-Wimplicit-function-declaration]
 if(k==1)l[min(x,y)]++,r[max(x,y)]++;
           ^~~
/in/foo.c:16:25: warning: implicit declaration of function 'max' [-Wimplicit-function-declaration]
 if(k==1)l[min(x,y)]++,r[max(x,y)]++;
                         ^~~