1988 AJHSME #16
Source:
June 21, 2011
Problem Statement
[asy]
for(int a=0; a<4; ++a)
{
draw((a,0)--(a,3));
}
for(int b=0; b<4; ++b)
{
draw((0,b)--(3,b));
}[/asy]Placing no more than one in each small square, what is the greatest number of 's that can be put on the grid shown without getting three 's in a row vertically, horizontally, or diagonally?