View Compilation Error

246914_0_6640.cpp: In function `int main()':
246914_0_6640.cpp:7: error: `s1' undeclared (first use this function)
246914_0_6640.cpp:7: error: (Each undeclared identifier is reported only once for each function it appears in.)
246914_0_6640.cpp:7: error: `s2' undeclared (first use this function)