#pragma GCC optimize ("Ofast") #include using namespace std; inline int my_getchar(){ static char buf[1048576]; static int s = 1048576; static int e = 1048576; if(s == e && e == 1048576){ e = fread(buf, 1, 1048576, stdin); s = 0; } if(s == e){ return EOF; } return buf[s++]; } inline void rd(long long &x){ int k; int m=0; x=0; for(;;){ k = my_getchar(); if(k=='-'){ m=1; break; } if('0'<=k&&k<='9'){ x=k-'0'; break; } } for(;;){ k = my_getchar(); 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(buf, 1, s, stdout); } } } ; MY_WRITER MY_WRITER_VAR; void my_putchar(int a){ if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){ fwrite(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(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('-'); } while(s--){ my_putchar(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(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('-'); } while(s--){ my_putchar(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(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('E'); my_putchar('r'); my_putchar('r'); return; } if(x < 0){ my_putchar('-'); 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(k + '0'); } if(d > 0){ my_putchar('.'); 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(k + '0'); } } } inline void wt_L(const char c[]){ int i=0; for(i=0;c[i]!='\0';i++){ my_putchar(c[i]); } } inline void wt_L(string &x){ int i=0; for(i=0;x[i]!='\0';i++){ my_putchar(x[i]); } } template inline S divup_L(S a, T b){ return (a+b-1)/b; } int main(){ long long N; rd(N); long long H; rd(H); long long W; rd(W); wt_L((N/2)*((divup_L(N,2))) * (H+W-2)); wt_L('\n'); return 0; } // cLay version 20210405-1 // --- original code --- // //no-unlocked // { // ll @N, @H, @W; // wt( (N/2)*(N/+ 2) * (H+W-2)); // }