Add missing include.

[Hawk777]

std::cerr is used in a few places; in a debug build iostream seems to be included from one of the other headers, but in a release built it isn't, so it should be included here.

[teruteru2451]

include

int main() { printf("hello,world!\n"); printf("RPG game.\n"); int a = 120 ; int b = 20 ; printf("enemy's HP = %d\n",a); printf("attack %d\n",b); printf(); return 0; }

[teruteru2451]

include

int main() { printf("hello,world!\n"); printf("RPG game.\n"); int a = 120 ; int b = 20 ; printf("enemy's HP = %d\n",a); printf("attack %d\n",b); printf(); return 0; }