#import<set>
int n,i,j,a[500],b[500];main(){std::set<double>s;for(scanf("%d%d%d",&n,&a[0],&b[0]);i<n;)j<i?s.insert(b[i]-b[j]?(a[i]-a[j])*1./(b[i]-b[j]):n),j++:j=0&++i&scanf("%d%d",&a[i],&b[i]);printf("%d",s.size()*2);}
./Main.cpp:1:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
1 | #import<set>
| ^~~~~~
./Main.cpp:2:30: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type]
2 | int n,i,j,a[500],b[500];main(){std::set<double>s;for(scanf("%d%d%d",&n,&a[0],&b[0]);i<n;)j<i?s.insert(b[i]-b[j]?(a[i]-a[j])*1./(b[i]-b[j]):n),j++:j=0&++i&scanf("%d%d",&a[i],&b[i]);printf("%d",s.size()*2);}
| ^
./Main.cpp: In function ‘int main()’:
./Main.cpp:2:151: warning: operation on ‘i’ may be undefined [-Wsequence-point]
2 | int n,i,j,a[500],b[500];main(){std::set<double>s;for(scanf("%d%d%d",&n,&a[0],&b[0]);i<n;)j<i?s.insert(b[i]-b[j]?(a[i]-a[j])*1./(b[i]-b[j]):n),j++:j=0&++i&scanf("%d%d",&a[i],&b[i]);printf("%d",s.size()*2);}
| ^~~
./Main.cpp:2:190: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘std::set<double>::size_type’ {aka ‘long unsigned int’} [-Wformat=]
2 | int n,i,j,a[500],b[500];main(){std::set<double>s;for(scanf("%d%d%d",&n,&a[0],&b[0]);i<n;)j<i?s.insert(b[i]-b[j]?(a[i]-a[j])*1./(b[i]-b[j]):n),j++:j=0&++i&scanf("%d%d",&a[i],&b[i]);printf("%d",s.size()*2);}
| ~^ ~~~~~~~~~~
| | |
| int std::set<double>::size_type {aka long unsigned int}
|...