Main.cc: In function 'int main()': Main.cc:10:22: warning: left operand of comma operator has no effect [-Wunused-value] printf<<( "max=%d", c); ^ Main.cc:10:23: error: invalid operands of types 'int(const char*, ...)' and 'int' to binary 'operator<<' printf<<( "max=%d", c); ^ Main.cc:5:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d,%d", &a, &b); ^