A person is swimming with a speed of $10 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ at an angle of $120 ^ { \circ }$ with the flow and reaches to a point directly opposite on the other side of the river. The speed of the flow is $x \mathrm {~m} \mathrm {~s} ^ { - 1 }$. The value of $x$ to the nearest integer is $\_\_\_\_$.