prepare (1/3): 
finished

make (2/3): 
g++ -g -Wall -O2 -std=c++11 -o main.o -c main.cpp
g++ -g -Wall -O2 -std=c++11 -o graph.o -c graph.cpp
g++ -g -Wall -O2 -std=c++11 -o main main.o graph.o
finished

clean (3/3): 
finished

all task finished, build successfully