View Compilation Error

0_0_13112731_19251.cpp: In function 'int max(int, int, int)':
0_0_13112731_19251.cpp:10:21: error: 'swap' was not declared in this scope
     if(x<y) swap(x,y);  
                     ^
0_0_13112731_19251.cpp:11:21: error: 'swap' was not declared in this scope
     if(x<z) swap(x,z);  
                     ^