prepare (1/3): 
finished

make (2/3): 
Makefile:49: warning: overriding recipe for target 'main'
Makefile:21: warning: ignoring old recipe for target 'main'
Makefile:52: warning: overriding recipe for target 'memcheck'
Makefile:24: warning: ignoring old recipe for target 'memcheck'
Makefile:55: warning: overriding recipe for target 'clean'
Makefile:27: warning: ignoring old recipe for target 'clean'
g++ -g -Wall -o main.o -c main.cpp
main.cpp: In function 'int main(int, char**)':
main.cpp:61:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<m;i++){
                 ~^~
main.cpp:64:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j=0;j<n;j++){
                 ~^~
main.cpp:65:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<m;i++){
                     ~^~
main.cpp:92:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (x < 0 || x >= m || y < 0 || y >= n) continue;
                          ~~^~~~
main.cpp:92:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (x < 0 || x >= m || y < 0 || y >= n) continue;
                                             ~~^~~~
g++ -g -Wall -o main main.o
finished

clean (3/3): 
finished

all task finished, build successfully