foo.cpp: In function 'int cal(std::string, int, int, int)':
foo.cpp:41:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
foo.cpp:68:39: error: 'abs' was not declared in this scope
foo.cpp:68:39: note: suggested alternative:
In file included from foo.cpp:3:0:
c:\mingw32\bin\../lib/gcc/mingw32/4.7.1/include/c++/cmath:102:5: note:   'std::abs'
foo.cpp:81:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
foo.cpp:107:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
foo.cpp: In function 'int main()':
foo.cpp:170:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
foo.cpp:201:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]