foo.cpp:4:9: error: 'll' does not name a type
 typedef ll long long;
         ^
foo.cpp:5:1: error: 'll' does not name a type
 ll exgcd(ll a,ll b,ll &x,ll &y){
 ^
foo.cpp: In function 'int main()':
foo.cpp:13:5: error: 'll' was not declared in this scope
     ll a,b,x=0,y=0;
     ^
foo.cpp:14:10: error: 'a' was not declared in this scope
     cin>>a>>b;
          ^
foo.cpp:14:13: error: 'b' was not declared in this scope
     cin>>a>>b;
             ^
foo.cpp:15:15: error: 'x' was not declared in this scope
     exgcd(a,b,x,y);
               ^
foo.cpp:15:17: error: 'y' was not declared in this scope
     exgcd(a,b,x,y);
                 ^
foo.cpp:15:18: error: 'exgcd' was not declared in this scope
     exgcd(a,b,x,y);
                  ^