#pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #pragma GCC optimize("inline") #include using namespace std; template struct cLtraits_identity{ using type = T; } ; template using cLtraits_try_make_signed = typename conditional< is_integral::value, make_signed, cLtraits_identity >::type; template struct cLtraits_common_type{ using tS = typename cLtraits_try_make_signed::type; using tT = typename cLtraits_try_make_signed::type; using type = typename common_type::type; } ; void*wmem; char memarr[96000000]; template inline auto min_L(S a, T b) -> typename cLtraits_common_type::type{ return (typename cLtraits_common_type::type) a <= (typename cLtraits_common_type::type) b ? a : b; } template inline void walloc1d(T **arr, int x, void **mem = &wmem){ static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1}; (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] ); (*arr)=(T*)(*mem); (*mem)=((*arr)+x); } template inline void walloc1d(T **arr, int x1, int x2, void **mem = &wmem){ walloc1d(arr, x2-x1, mem); (*arr) -= x1; } inline int my_getchar_unlocked(){ static char buf[1048576]; static int s = 1048576; static int e = 1048576; if(s == e && e == 1048576){ e = fread_unlocked(buf, 1, 1048576, stdin); s = 0; } if(s == e){ return EOF; } return buf[s++]; } inline void rd(int &x){ int k; int m=0; x=0; for(;;){ k = my_getchar_unlocked(); if(k=='-'){ m=1; break; } if('0'<=k&&k<='9'){ x=k-'0'; break; } } for(;;){ k = my_getchar_unlocked(); if(k<'0'||k>'9'){ break; } x=x*10+k-'0'; } if(m){ x=-x; } } struct MY_WRITER{ char buf[1048576]; int s; int e; MY_WRITER(){ s = 0; e = 1048576; } ~MY_WRITER(){ if(s){ fwrite_unlocked(buf, 1, s, stdout); } } } ; MY_WRITER MY_WRITER_VAR; void my_putchar_unlocked(int a){ if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){ fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout); MY_WRITER_VAR.s = 0; } MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a; } inline void wt_L(char a){ my_putchar_unlocked(a); } inline void wt_L(int x){ int s=0; int m=0; char f[10]; if(x<0){ m=1; x=-x; } while(x){ f[s++]=x%10; x/=10; } if(!s){ f[s++]=0; } if(m){ my_putchar_unlocked('-'); } while(s--){ my_putchar_unlocked(f[s]+'0'); } } inline void wt_L(unsigned x){ int s=0; char f[10]; while(x){ f[s++]=x%10; x/=10; } if(!s){ f[s++]=0; } while(s--){ my_putchar_unlocked(f[s]+'0'); } } inline void wt_L(long long x){ int s=0; int m=0; char f[20]; if(x<0){ m=1; x=-x; } while(x){ f[s++]=x%10; x/=10; } if(!s){ f[s++]=0; } if(m){ my_putchar_unlocked('-'); } while(s--){ my_putchar_unlocked(f[s]+'0'); } } inline void wt_L(unsigned long long x){ int s=0; char f[21]; while(x){ f[s++]=x%10; x/=10; } if(!s){ f[s++]=0; } while(s--){ my_putchar_unlocked(f[s]+'0'); } } int WRITER_DOUBLE_DIGIT = 15; inline int writerDigit_double(){ return WRITER_DOUBLE_DIGIT; } inline void writerDigit_double(int d){ WRITER_DOUBLE_DIGIT = d; } inline void wt_L(double x){ const int d = WRITER_DOUBLE_DIGIT; int k; int r; double v; if(x!=x || (x==x+1 && x==2*x)){ my_putchar_unlocked('E'); my_putchar_unlocked('r'); my_putchar_unlocked('r'); return; } if(x < 0){ my_putchar_unlocked('-'); x = -x; } x += 0.5 * pow(0.1, d); r = 0; v = 1; while(x >= 10*v){ v *= 10; r++; } while(r >= 0){ r--; k = floor(x / v); if(k >= 10){ k = 9; } if(k <= -1){ k = 0; } x -= k * v; v *= 0.1; my_putchar_unlocked(k + '0'); } if(d > 0){ my_putchar_unlocked('.'); v = 1; for(r=(0);r<(d);r++){ v *= 0.1; k = floor(x / v); if(k >= 10){ k = 9; } if(k <= -1){ k = 0; } x -= k * v; my_putchar_unlocked(k + '0'); } } } inline void wt_L(const char c[]){ int i=0; for(i=0;c[i]!='\0';i++){ my_putchar_unlocked(c[i]); } } inline void wt_L(string &x){ int i=0; for(i=0;x[i]!='\0';i++){ my_putchar_unlocked(x[i]); } } template int coordcomp_L(int n1, T arr1[], int n2, T arr2[], int res1[] = NULL, int res2[] = NULL, void *mem = wmem){ int i; int k = 0; pair*r; walloc1d(&r, n1+n2, &mem); for(i=(0);i<(n1);i++){ r[i].first = arr1[i]; r[i].second = i; } for(i=(0);i<(n2);i++){ r[n1+i].first = arr2[i]; r[n1+i].second = n1+i; } sort(r, r+n1+n2); for(i=(0);i<(n1+n2);i++){ if(i && r[i].first != r[i-1].first){ k++; } if(r[i].second < n1){ if(res1!=NULL){ res1[r[i].second] = k; } else{ arr1[r[i].second] = k; } } else{ if(res2!=NULL){ res2[r[i].second-n1] = k; } else{ arr2[r[i].second-n1] = k; } } } return k+1; } template struct fenwick{ int size; int memory; T*data; void malloc(int mem); void malloc(int mem, int fg); void walloc(int mem, void **workMemory = &wmem); void walloc(int mem, int fg, void **workMemory = &wmem); void free(void); void init(int N); void add(int k, T val); T get(int k); T range(int a, int b); int kth(T k); } ; long long inversion_range(int N, int A[], int mn, int mx, void *mem=wmem){ int i; int j; int k; long long res = 0; fenwick t; t.walloc(mx-mn+1, &mem); t.init(mx-mn+1); for(i=N-1;i>=0;i--){ res += t.get(A[i]-mn-1); t.add(A[i]-mn,1); } return res; } template long long inversion(int N, T A[], void *mem=wmem){ int i; int j; int k; int p; int n1; int n2; T*x; T*y; long long res = 0; walloc1d(&x, N, &mem); walloc1d(&y, N, &mem); for(i=(0);i<(N);i++){ x[i] = A[i]; } for(k=0;k x[k+i]){ swap(x[k+i-1], x[k+i]); res++; } } } } p = 4; while(p long long inversion(int N, T A[], T B[], void *mem = wmem){ int i; int k; int sz; int*aa; int*bb; int*hist1; int*hist2; int**ind; walloc1d(&aa, N, &mem); walloc1d(&bb, N, &mem); sz =coordcomp_L(N,A,N,B,aa,bb,mem); if(sz > N){ return -1; } walloc1d(&hist1, sz, &mem); walloc1d(&hist2, sz, &mem); for(i=(0);i<(sz);i++){ hist1[i] = 0; } for(i=(0);i<(sz);i++){ hist2[i] = 0; } for(i=(0);i<(N);i++){ hist1[aa[i]]++; } for(i=(0);i<(N);i++){ hist2[bb[i]]++; } for(i=(0);i<(sz);i++){ if(hist1[i] != hist2[i]){ return -1; } } walloc1d(&ind, sz, &mem); for(i=(0);i<(sz);i++){ walloc1d(&ind[i], hist2[i], &mem); } for(i=(0);i<(sz);i++){ hist2[i] = 0; } for(i=(0);i<(N);i++){ k = bb[i]; ind[k][hist2[k]++] = i; } for(i=(N)-1;i>=(0);i--){ k = aa[i]; aa[i] = ind[k][--hist1[k]]; } return inversion_range(N,aa,0,N-1,mem); } int N; int P[3000]; int r[3000]; int main(){ int i; wmem = memarr; rd(N); { int Lj4PdHRW; for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){ rd(P[Lj4PdHRW]);P[Lj4PdHRW] += (-1); } } for(i=(0);i<(N);i++){ r[P[i]] = i; } wt_L(inversion(N,r)); wt_L('\n'); return 0; } template void fenwick::malloc(int mem){ memory = mem; data = (T*)std::malloc(sizeof(T)*mem); } template void fenwick::malloc(int mem, int fg){ memory = mem; data = (T*)std::malloc(sizeof(T)*mem); if(fg){ init(mem); } } template void fenwick::walloc(int mem, void **workMemory /* = &wmem*/){ memory = mem; walloc1d(&data, mem, workMemory); } template void fenwick::walloc(int mem, int fg, void **workMemory /* = &wmem*/){ memory = mem; walloc1d(&data, mem, workMemory); if(fg){ init(mem); } } template void fenwick::free(void){ memory = 0; free(data); } template void fenwick::init(int N){ size = N; memset(data,0,sizeof(T)*N); } template void fenwick::add(int k, T val){ while(k < size){ data[k] += val; k |= k+1; } } template T fenwick::get(int k){ T res = 0; while(k>=0){ res += data[k]; k = (k&(k+1))-1; } return res; } template T fenwick::range(int a, int b){ if(a < 0){ a = 0; } if(b >= size){ b = size - 1; } if(b < a){ return 0; } return get(b) - get(a-1); } template int fenwick::kth(T k){ int i=0; int j=size; int c; T v; while(i