Ural 1052

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>#include<queue>using namespace std;#define nMax 500#define LL long longtypedef pair<int,int> point ;#define x first#define y seconddouble const eps = 1e-9;int dcmp(double x) {if(fabs(x)<=eps) return 0;return x > 0 ? 1 : -1;}double det(point a,point b,point c) {return (b.x-a.x)*(c.y-b.y) - (b.y-a.y)*(c.x-b.x);}typedef pair<point,point> line;int dot_online(point a,line l) {return det (a,l.x,l.y) == 0;}point p[nMax];int n;int main () {scanf("%d",&n);for(int i=0;i<n;i++) scanf("%d%d",&p[i].x,&p[i].y);int ret = -1;for(int i=0;i<n;i++) {for(int j=i+1;j<n;j++) {line l(p[i],p[j]);int sum = 0;for(int k=0;k<n;k++) if(dot_online(p[k],l)) sum ++;if(sum > ret) ret = sum;}}printf("%d\n",ret);return 0;}