#include #include #define n 1000000000 int main() #if 0 { int t[n], i, j, c=0; for(i=n;i--;) t[i]=i; for(i=2;j=i*i,j1;) c+=t[i]==i; #elif 1 { int i, j, c=0, m=n/2; char *t=malloc(m*sizeof(*t)); for(i=m;i--;) t[i]=1; for(i=3;j=i*i/2,j0; for(i=2;i