View Compilation Error

0_0_4674263_10941.cpp: In function `int main()':
0_0_4674263_10941.cpp:21: error: `S' undeclared (first use this function)
0_0_4674263_10941.cpp:21: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4674263_10941.cpp:22: error: expected `;' before "if"